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feat: add lab2 

feat: add lab2 solution
feat: add week2 note
feat: add week2 lec
Co-authored-by: MayGe <152044636+M4yGem1ni@users.noreply.github.com>
Co-authored-by: EQ1932 <145545663+EQ1932@users.noreply.github.com>
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focused_xy 2024-10-14 14:13:09 +08:00
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# Lab2 C 语言基本语法
## Lab2_1 C 语言基本语法
- 完成lab2_1中的四个.c文件
- 请根据每个ex_中的TODO完成内容。
- 你可以使用 make 自动编译可执行文件
```bash
make # 编译所有可执行文件
make ex1_ptr # 仅编译 ex1_ptr.c
./ex1_ptr # 运行 ex1_ptr
make clean # 删除可执行文件
```
## Lab2_2 字符串和循环
- 本实验使用了参数char *argv[]，请在编译后尝试向程序输入命令行参数，如:
```bash
make
./str_and_cyc California Oregon Washington Texas
```
输出内容，如下所示:
```bash
for:
arg 1: California
arg 2: Oregon
arg 3: Washington
arg 4: Texas
state 0: California
state 1: Oregon
state 2: Washington
state 3: Texas
while:
arg 0: ./str_and_cyc
arg 1: California
arg 2: Oregon
arg 3: Washington
arg 4: Texas
state 0: California
state 1: Oregon
state 2: Washington
state 3: Texas
```
- 请对srt_and_cyc.c文件中的for和while循环尝试以下操作并查看结果。
- for循环
- 将i初始化为0看看会发生什么。是否也需要改动argc，不改动的话它能正常工作吗？为什么下标从0开始可以正常工作？
- 将num_states改为错误的值(使它变大)，来看看会发生什么。
- RTFM: NULL是什么东西，尝试将它用做states的一个元素，看看它会打印出什么。
- 看看你是否能在打印之前将states的一个元素赋值给argv中的元素，再试试相反的操作。
- while循环
- 使用while循环将argv中的值复制到states。
- 让这个复制循环不会执行失败，即使argv之中有很多元素也不会全部放进states。
- 研究你是否真正复制了这些字符串。答案可能会让你感到意外和困惑。
## 递归(可选，难度较大)
- 经典递归例子
```C
#include <stdio.h>
int fibonacci(int n) {
if (n < 1) {
return -1;
}
if (n == 1 || n == 2) {
return 1;
}
else {
return fibonacci(n - 1) + fibonacci(n - 2);
}
}
int main(void)
{
int a;
while (scanf("%d", &a) != EOF) {
printf("Fibonacci数列第%d项为:%d\n", a, fibonacci(a));
}
return 0;
}
```
- 理解递归的重要方式
- Base Case：递归主体以一个基本情况开始，通常它是这个条件语句，定义了函数对最简单的输入的行为，并通常被用作递归结束的出口。
- Recursive Calls：在Base Case之后，是一个或多个递归调用。递归调用总是有一个特点：它们简化了原来的问题。
- 数学归纳法理解：
1. 验证递归函数`F(X)`取Base Case时成立.
2. 假设X = n时成立，那么可以推导出在X = n+1时递归函数`F(X)`做出正确的行为。
3. 最后一步总结表述。
- 数独
- 数独（Sudoku）是一种经典的逻辑数字游戏，通常由一个9x9的网格组成，这个网格被进一步划分为9个3x3的小方块。游戏的目标是通过填充数字1到9，使得每一行、每一列和每一个3x3的小方块都包含数字1到9，且数字不能重复。
- 实现一个递归函数`bool solveSudoku(int board[N][N], int row, int col)`判断数独是否可解，有解则填充正确答案。
- 题中数独采用二维数组，需解答填充的数字用0代替如：
0 6 0 0 0 0 0 7 1
7 0 5 4 0 3 0 0 0
0 0 0 6 7 0 3 0 0
0 3 7 2 4 1 8 6 0
0 0 0 0 0 5 1 9 0
1 5 8 7 9 0 2 3 0
6 0 1 0 2 0 0 0 3
0 7 9 0 0 0 5 0 2
0 0 0 0 0 4 7 0 0
提供了`printBoard(int board[N][N])`函数打印数独和`isSafe(int board[N][N], int row, int col, int num)`函数检查数字是否可以放在board[row][col]位置。
- 运行judge.sh检测程序正确性。
- 完成文件`sudoku.c`中的`solveSudoku`函数编写。

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Others/Codes/Lecture1/hello-world.c → Lectures/Lecture1/Codes/hello-world.c
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@ -1,5 +1,5 @@
CC := gcc
CFLAGS := -Wall -Werror -Wpedantic -g -std=c11
CFLAGS := -Wall -Wextra -Werror -g -std=c11
TARGET := float hello-world
all: $(TARGET)

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Lectures/Lecture2/Codes/1-control-flow.c Normal file
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/* C 语言中的控制流 */
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char *argv[]) {
// 条件分支
// if else
if (argc == 1) {
printf("args = NULL\n");
} else if (argc == 2) {
printf("args = %d\n", argc - 1);
printf("argv:%s\n", argv[1]);
} else {
printf("args = %d\n", argc - 1);
}
printf("\n");
// switch
switch (argc) {
case 1:
printf("args = NULL\n");
break;
case 2:
printf("args = %d\n", argc - 1);
printf("argv:%s\n", argv[1]);
break;
default:
printf("args = %d\n", argc - 1);
break;
}
// 三元表达式
argc == 2 ? printf("yes\n\n") : printf("no\n\n");
// 循环结构
int i = 10;
while (i != 0) {
printf("%d ", i);
i--;
}
printf("\n");
do {
printf("%d ", i);
i++;
} while (i < 10);
printf("\n");
for (i = 0; i < 10; i++) {
printf("%d ", i);
}
printf("\n\n");
// 跳转控制语句
/**
* @statement break; 跳出循环或者是跳出switch语句
* @statement continue; 跳过下面的步骤重新开始下一次循环
*/
printf("goto语句示范:\n");
int go = 0;
lable:
printf("%d ", go);
if (go < 3) {
go++;
goto lable;
}
printf("\n");
return EXIT_SUCCESS;
}

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Lectures/Lecture2/Codes/2-function.c Normal file
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#include <stdio.h>
#include <stdlib.h>
// 函数声明
int fact(int);
int main(void) {
printf("%d", fact(5));
return EXIT_SUCCESS;
}
// 函数定义
int fact(int n) {
if (n <= 1) {
return 1;
}
int sum = 1, i;
for (i = 1; i <= n; i++) {
sum *= i;
}
return sum;
}

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Lectures/Lecture2/Codes/3-array.c Normal file
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#include <stdio.h>
#include <stdlib.h>
int main(void) {
// 定义
unsigned char temp[10] = {0x11, 0x15, 0x22};
// 数组的地址
printf("temp address: %p\n", temp);
// 更改
temp[3] = 0xa8;
// 使用
for (size_t i = 0; i < 10; i++) {
printf("%02x ", temp[i]);
}
printf("\n");
return EXIT_SUCCESS;
}

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Lectures/Lecture2/Codes/4-string.c Normal file
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/* 字符串以'\0'结尾 */
int main(void) {
char str1[] = "I Can Eat Glass";
char str2[20] = "I Can Eat Glass";
printf("str1:%s\nsize:%lu\nstr2:%s\nsize:%lu\n", str1, strlen(str1), str2,
strlen(str2));
return EXIT_SUCCESS;
}

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Lectures/Lecture2/Codes/5-string-advance.c Normal file
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/* string.h标准库的几个常用函数 */
int main(void) {
char str1[] = "I Can Eat Glass";
char str2[] = "Neko Bytes";
printf("str1:%s\nsize:%lu\nstr2:%s\nsize:%lu\n", str1, strlen(str1), str2,
strlen(str2));
// 字符串比较
int h = strcmp(str1, str2);
if (h != 0) {
if (h > 0) {
printf("str1更大\n");
} else {
printf("str2更大\n");
}
} else {
printf("str1和str2一样大\n");
}
// 字符串赋值
strcpy(str1, "I love windows\n");
printf("str1:%s", str1);
return EXIT_SUCCESS;
}

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Lectures/Lecture2/Codes/6-macro.c Normal file
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#include <stdio.h>
#define MAX 1000
int main(void) {
printf("MAX: %d", MAX);
return 0;
}

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Lectures/Lecture2/Codes/7-variable.c Normal file
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@ -0,0 +1,13 @@
#include <stdio.h>
int main(void) {
unsigned int a;
int b;
float c;
printf("a,b,c各元素的值\n");
printf("%u %d %f\n", a, b, c);
printf("a,b,c各元素的地址\n");
printf("%p %p %p\n", &a, &b, &c);
return 0;
}

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Lectures/Lecture2/Codes/8-nested-array.c Normal file
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@ -0,0 +1,11 @@
#include <stdio.h>
int main(void) {
int matrix[2][2] = {{1, 2}, {3, 4}};
printf("%p %p %p %p\n", &matrix[0][0], &matrix[0][1], &matrix[1][0],
&matrix[1][1]);
printf("sizeof matrix: %zu\n", sizeof matrix);
printf("sizeof matrix[0]: %zu\n", sizeof matrix[0]);
printf("sizeof matrix[1]: %zu\n", sizeof matrix[1]);
return 0;
}

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Lectures/Lecture2/Codes/9-pointer.c Normal file
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#include <stdio.h>
void swap1(int x, int y) {
int t = x;
x = y;
y = t;
}
void swap2(int *x, int *y) {
int t = *x;
*x = *y;
*y = t;
}
int main(void) {
int a = 1, b = 2;
printf("a = %d, b = %d\n", a, b);
swap1(a, b);
printf("a = %d, b = %d after swap1\n", a, b);
swap2(&a, &b);
printf("a = %d, b = %d after swap2\n", a, b);
return 0;
}

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Lectures/Lecture2/Codes/B-pointer-clac.c Normal file
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@ -0,0 +1,14 @@
#include <stdio.h>
int main(void) {
int array[10] = {0};
printf("array = %p\n", array);
int *p1 = array, *p2 = array;
printf("p1 = %p, p2 = %p\n", p1, p2);
p1 = p1 + 1;
printf("p1 = %p, p2 = %p\n", p1, p2);
p2 = p2 + 9;
printf("p1 = %p, p2 = %p\n", p1, p2);
printf("p2 - p1 = %u\n", (unsigned int)(p2 - p1));
return 0;
}

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Lectures/Lecture2/Codes/README.md Normal file
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@ -0,0 +1,7 @@
在本目录下打开终端,输入:
```bash
make
```
在`./build`目录下生成对应的可执行文件

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Lectures/Lecture2/Codes/makefile Normal file
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BUILD_DIR = ./build
CC := gcc
CFLAGS := -Wall -Wextra -g -std=c11
SRCS := $(wildcard *.c)
TARGETS := $(SRCS:%.c=$(BUILD_DIR)/%)
all: $(TARGETS)
$(BUILD_DIR)/%: %.c
@mkdir -p $(dir $@)
$(CC) $(CFLAGS) -o $@ $<
clean:
-rm -rf $(BUILD_DIR)
.PHONY: clean all

784
Lectures/Lecture2/Lecture2/index.html
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@ -12,7 +12,7 @@
type="text/css">
<title> Lecture3 </title>
<!-- browser favicon -->
<link rel="shortcut icon" href="./static/img/favicon.ico">
<link rel="shortcut icon" href="./static/img/favicon.png">
<style>
.font-sans {
font-family: 'Lato', 'SimHei', 'STHeiti', 'SimHei', 'Serif';
@ -22,9 +22,15 @@
font-family: 'Source Serif Pro', 'Songti SC', 'SimSun', 'Serif', serif;
}
</style>
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crossorigin="anonymous"></script> -->
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<script src="plugin/markdown/markdown.js"></script>
<script>
document.addEventListener("DOMContentLoaded", function () {
renderMathInElement(document.body, {
@ -52,67 +58,114 @@
<div class="reveal">
<div class="slides">
<section><section><div class="center middle"><div style="width:100%"><div><h1 id="c" class="text-2xl mt-2 font-sans">C 语言基础语法</h1><p class="font-serif my-1">
<include src="Slides_Author">
<div class="py-16">
<p class="font-serif my-1">
<a href="https://github.com/M4yGem1ni" class=" text-amber-900">
M4yGem1ni
</a>
</p>
</div>
<div class="row">
<p class="font-serif my-1"/>
<section>
<section>
<div class="center middle">
<div style="width:100%">
<div>
<h1 id="c" class="text-2xl mt-2 font-sans">C 语言基础语法</h1>
<p class="font-serif my-1">
<include src="Slides_Author">
<div class="py-16">
<p class="font-serif my-1">
<a href="https://github.com/M4yGem1ni" class=" text-amber-900">
M4yGem1ni
</a>
</p>
</div>
<div class="row">
<p class="font-serif my-1" />
<div class="author-affiliation">
<a href="https://github.com/E1PsyCongroo/NekoBytes-TheMissing" class=" text-amber-900">
<p class="font-serif my-1">
NekoBytes
</p>
<img class="inline-img h-24" src="./static/img/66763c573c4c496bb6f09e2846e59de6.svg" style="display: inline-block;"/>
</a>
</div>
<div class="author-affiliation">
<a href="https://github.com/E1PsyCongroo/NekoBytes-TheMissing"
class=" text-amber-900">
<p class="font-serif my-1">
NekoBytes
</p>
<img class="inline-img h-24"
src="./static/img/505d39ab3d4a4f969b90552a6c5477cc.svg"
style="display: inline-block;" />
</a>
</div>
</div>
</include>
</p></div></div></div></section></section><section><section><div><h2 id="agenda-part-1" class="text-xl mt-2 pb-2 font-sans">Agenda Part 1</h2>
<p class="font-serif my-1"><img class="float-right" src="./static/img/63614731af7e4930ac3b8f45cc6b2e44.png" width=""/></p>
<ul class="list-disc font-serif">
<li class="ml-8">计算机科学抽象思维</li>
<li class="ml-8">C语言常量</li>
<li class="ml-8">C中的控制流</li>
<li class="ml-8">函数</li>
<li class="ml-8">数组</li>
<li class="ml-8">字符串</li>
<li class="ml-8">宏定义与预处理</li>
</ul></div></section><section><div><h2 id="_1" class="text-xl mt-2 pb-2 font-sans">抽象是什么？能吃吗</h2>
<ul class="list-disc font-serif">
<li class="ml-8">抽象好比是一个黑箱，我们不需要知道中间发生的过程，只需要知道我输入了什么，我能输出什么，最简单的例子就是 <code>printf</code>。</li>
</ul>
<p class="font-serif my-1"><img class="float-center" src="./static/img/05b06177e02440f4957a387c50507e20.png" width=""/>
<img class="float-center" src="./static/img/8a29491886574f1cb6af2da1f77bb829.png" width=""/>
<img class="float-center" src="./static/img/60381f9c9e444d2cacd7458c6babd353.png" width=""/></p></div></section><section><div><h2 id="_1" class="text-xl mt-2 pb-2 font-sans">编程本身就是一种抽象</h2>
<ul class="list-disc font-serif">
<li class="ml-8">我们使用的编程语言，比如C语言和Python，都是抽象，因为计算机只懂二进制。</li>
</ul>
<p class="font-serif my-1"><img alt="抽象" src="./static/img/8fd69852d3f14e008b126f72aae93328.png"/>
</p><center>
<img class="inline" src="./static/img/45025d0dd00b40458caeef05daef1884.png" width="45%"/>
<img class="inline" src="./static/img/80a5b2eae1c046d3ae60ea5547588073.png" width="45%"/>
</center></div></section><section><div><h2 id="_1" class="text-xl mt-2 pb-2 font-sans">抽象的力量</h2>
<p class="font-serif my-1"><a href="https://www.2048.org">https://www.2048.org</a>
这是一个2048
我们可以将其分解为以下几个模块</p>
<ul class="list-disc font-serif">
<li class="ml-8">游戏板: board[BOARD_SIZE][BOARD_SZIE]</li>
<li class="ml-8">初始化: initialize_board</li>
<li class="ml-8">随机生成: generator_number</li>
<li class="ml-8">打印显示: print_board</li>
<li class="ml-8">读取移动指令: choose_direction</li>
<li class="ml-8">合并并移动: move_and_merge</li>
<li class="ml-8">判断游戏终止: is_finished</li>
</ul></div></section><section><div><h2 id="_1" class="text-xl mt-2 pb-2 font-sans">抽象的力量</h2>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="n">run_game</span><span class="p">()</span><span class="w"> </span><span class="p">{</span>
</div>
</include>
</p>
</div>
</div>
</div>
</section>
</section>
<section>
<section>
<div>
<h2 id="agenda-part-1" class="text-xl mt-2 pb-2 font-sans">Agenda Part 1</h2>
<p class="font-serif my-1"><img class="float-right"
src="./static/img/f7640ea9a80d4963bfe259c5f15245f6.png" width="" /></p>
<ul class="list-disc font-serif">
<li class="ml-8">计算机科学抽象思维</li>
<li class="ml-8">C语言常量</li>
<li class="ml-8">C中的控制流</li>
<li class="ml-8">函数</li>
<li class="ml-8">数组</li>
<li class="ml-8">字符串</li>
<li class="ml-8">宏定义与预处理</li>
</ul>
</div>
</section>
<section>
<div>
<h2 id="_1" class="text-xl mt-2 pb-2 font-sans">抽象是什么？能吃吗</h2>
<ul class="list-disc font-serif">
<li class="ml-8">抽象好比是一个黑箱，我们不需要知道中间发生的过程，只需要知道我输入了什么，我能输出什么，最简单的例子就是 <code>printf</code>。
</li>
</ul>
<p class="font-serif my-1"><img class="float-center"
src="./static/img/eb0c14e67ede4c6982f672d1f23f8347.png" width="" />
<img class="float-center" src="./static/img/04c55e39a9fa4c7aa2edca121fb4bc52.png"
width="" />
<img class="float-center" src="./static/img/16a82e9965414299a076175865f6bea8.png"
width="" />
</p>
</div>
</section>
<section>
<div>
<h2 id="_1" class="text-xl mt-2 pb-2 font-sans">编程本身就是一种抽象</h2>
<ul class="list-disc font-serif">
<li class="ml-8">我们使用的编程语言，比如C语言和Python，都是抽象，因为计算机只懂二进制。</li>
</ul>
<p class="font-serif my-1"><img alt="抽象"
src="./static/img/d48aeab415ac4fdea9b473afe3e429b7.png" />
</p>
<center>
<img class="inline" src="./static/img/baf1ff76a5814d75bf99e5b2725d95e3.png" width="45%" />
<img class="inline" src="./static/img/9697bafbcaf14e97872e3fe646a5af93.png" width="45%" />
</center>
</div>
</section>
<section>
<div>
<h2 id="_1" class="text-xl mt-2 pb-2 font-sans">抽象的力量</h2>
<p class="font-serif my-1"><a href="https://www.2048.org">https://www.2048.org</a>
这是一个2048
我们可以将其分解为以下几个模块</p>
<ul class="list-disc font-serif">
<li class="ml-8">游戏板: board[BOARD_SIZE][BOARD_SZIE]</li>
<li class="ml-8">初始化: initialize_board</li>
<li class="ml-8">随机生成: generator_number</li>
<li class="ml-8">打印显示: print_board</li>
<li class="ml-8">读取移动指令: choose_direction</li>
<li class="ml-8">合并并移动: move_and_merge</li>
<li class="ml-8">判断游戏终止: is_finished</li>
</ul>
</div>
</section>
<section>
<div>
<h2 id="_1" class="text-xl mt-2 pb-2 font-sans">抽象的力量</h2>
<div class="codehilite">
<pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="n">run_game</span><span class="p">()</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">initialize_board</span><span class="p">();</span>
<span class="w"> </span><span class="n">generator_number</span><span class="p">();</span><span class="w"> </span><span class="n">generator_number</span><span class="p">();</span>
<span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="nb">true</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
@ -127,55 +180,73 @@
<span class="w"> </span><span class="n">print_board</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="p">}</span>
</code></pre></div></div></section><section><div><h2 id="_1" class="text-xl mt-2 pb-2 font-sans">变量</h2>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="k">typedef</span><span class="w"> </span><span class="kt">unsigned</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="kt">uint8_t</span><span class="p">;</span>
</code></pre></div>
</code></pre>
</div>
</div>
</section>
<section>
<div>
<h2 id="_1" class="text-xl mt-2 pb-2 font-sans">变量</h2>
<div class="codehilite">
<pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="k">typedef</span><span class="w"> </span><span class="kt">unsigned</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="kt">uint8_t</span><span class="p">;</span>
</code></pre>
</div>
<table>
<thead>
<tr>
<th>类型</th>
<th>描述</th>
<th>例子</th>
</tr>
</thead>
<tbody>
<tr>
<td>char</td>
<td>8位，ASCII</td>
<td>‘a’, ‘A’, ‘\n’, 12</td>
</tr>
<tr>
<td>int</td>
<td>整数值（正、负、0），&gt;= 16 位，一般为32位</td>
<td>0, 78, -217, 0x2E</td>
</tr>
<tr>
<td>unsigned int</td>
<td>整数值（正、0）</td>
<td>0, 6, 35102</td>
</tr>
<tr>
<td>short</td>
<td>整数值（正、负、0），&gt;= 16 位，一般为16位</td>
<td>0, -8, 32767</td>
</tr>
<tr>
<td>long</td>
<td>整数值（正、负、0），&gt;= 32 位，一般为32位</td>
<td>0, 78, -217, 301713123194</td>
</tr>
</tbody>
</table></div></section><section><div><h2 id="const" class="text-xl mt-2 pb-2 font-sans">Const 常量</h2>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="k">const</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">integer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">100</span><span class="p">;</span>
<table>
<thead>
<tr>
<th>类型</th>
<th>描述</th>
<th>例子</th>
</tr>
</thead>
<tbody>
<tr>
<td>char</td>
<td>8位，ASCII</td>
<td>‘a’, ‘A’, ‘\n’, 12</td>
</tr>
<tr>
<td>int</td>
<td>整数值（正、负、0），&gt;= 16 位，一般为32位</td>
<td>0, 78, -217, 0x2E</td>
</tr>
<tr>
<td>unsigned int</td>
<td>整数值（正、0）</td>
<td>0, 6, 35102</td>
</tr>
<tr>
<td>short</td>
<td>整数值（正、负、0），&gt;= 16 位，一般为16位</td>
<td>0, -8, 32767</td>
</tr>
<tr>
<td>long</td>
<td>整数值（正、负、0），&gt;= 32 位，一般为32位</td>
<td>0, 78, -217, 301713123194</td>
</tr>
</tbody>
</table>
</div>
</section>
<section>
<div>
<h2 id="const" class="text-xl mt-2 pb-2 font-sans">Const 常量</h2>
<div class="codehilite">
<pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="k">const</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">integer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">100</span><span class="p">;</span>
<span class="k">const</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="n">dob</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">1.20</span><span class="p">;</span>
<span class="k">const</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="n">MyChar</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">'c'</span><span class="p">;</span>
</code></pre></div>
</code></pre>
</div>
<ul class="list-disc font-serif">
<li class="ml-8">常量一经分配，无法更改。可以<a href="https://godbolt.org/z/eMWfK6Edq">尝试</a>添加<code>integer = 120;</code>看看会发生什么。</li>
</ul>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="cp">#include</span><span class="w"> </span><span class="cpf">&lt;stdio.h&gt;</span>
<ul class="list-disc font-serif">
<li class="ml-8">常量一经分配，无法更改。可以<a
href="https://godbolt.org/z/eMWfK6Edq">尝试</a>添加<code>integer = 120;</code>看看会发生什么。
</li>
</ul>
<div class="codehilite">
<pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="cp">#include</span><span class="w"> </span><span class="cpf">&lt;stdio.h&gt;</span>
<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">argc</span><span class="p">,</span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">argv</span><span class="p">[])</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">intager</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">100</span><span class="p">;</span>
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="n">dob</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">1.20</span><span class="p">;</span>
@ -185,41 +256,61 @@
<span class="w"> </span><span class="n">intager</span><span class="p">,</span><span class="n">dob</span><span class="p">,</span><span class="n">MyChar</span><span class="p">);</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span>
<span class="p">}</span>
</code></pre></div></div></section><section><div><h2 id="c" class="text-xl mt-2 pb-2 font-sans">C中的控制流</h2>
<ul class="list-disc font-serif">
<li class="ml-8">
<p class="font-serif my-1">语句(statement)可以是代码块 {} 或只是一个独立的语句</p>
<ul class="list-disc font-serif">
<li class="ml-8">if-else</li>
</ul>
<p class="font-serif my-1"><code>if (expr) statement</code></p>
<p class="font-serif my-1"><code>if (x == 0) y++;</code></p>
<p class="font-serif my-1"><code>if (x == 0) {y++;}</code></p>
<p class="font-serif my-1"><code>if (x == 0) {y++; j = j + y;}</code></p>
<p class="font-serif my-1"><code>if (expr) statement1 else statement2</code></p>
<ul class="list-disc font-serif">
<li class="ml-8">switch case</li>
<li class="ml-8">while: <code>while (expr) statement</code></li>
<li class="ml-8">for: <code>for (initialize; check; update) statement</code></li>
</ul>
</li>
</ul>
<p class="font-serif my-1"><a href="https://godbolt.org/z/6o31z4zPW">https://godbolt.org/z/6o31z4zPW</a></p></div></section><section><div><h2 id="_1" class="text-xl mt-2 pb-2 font-sans">函数</h2>
<ul class="list-disc font-serif">
<li class="ml-8">在编程中，函数是一段可重复使用的代码块，用于执行特定的任务或完成特定的操作。函数可以接受输入参数，并且可以返回一个值或执行一些操作</li>
<li class="ml-8">代码重用</li>
<li class="ml-8">提高代码可读性</li>
<li class="ml-8">提高代码可测试性（单元测试）</li>
<li class="ml-8">抽象</li>
</ul>
<p class="font-serif my-1"><a href="https://godbolt.org/z/11bxvT8Ga">https://godbolt.org/z/11bxvT8Ga</a></p></div></section><section><div><h2 id="_1" class="text-xl mt-2 pb-2 font-sans">数组</h2>
<ul class="list-disc font-serif">
<li class="ml-8">数组就是一整块变量的集合，数组名是数组存放的地址，使用索引确定每个元素的位置</li>
<li class="ml-8">定义：unsigned char temp[10] = {0x11,0x12,0x13};</li>
<li class="ml-8">使用：printf(“%02x ”,temp[0]);</li>
</ul>
<p class="font-serif my-1"><a href="https://godbolt.org/z/rzo6o1bsE">https://godbolt.org/z/rzo6o1bsE</a></p>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="cp">#include</span><span class="w"> </span><span class="cpf">&lt;stdio.h&gt;</span>
</code></pre>
</div>
</div>
</section>
<section>
<div>
<h2 id="c" class="text-xl mt-2 pb-2 font-sans">C中的控制流</h2>
<ul class="list-disc font-serif">
<li class="ml-8">
<p class="font-serif my-1">语句(statement)可以是代码块 {} 或只是一个独立的语句</p>
<ul class="list-disc font-serif">
<li class="ml-8">if-else</li>
</ul>
<p class="font-serif my-1"><code>if (expr) statement</code></p>
<p class="font-serif my-1"><code>if (x == 0) y++;</code></p>
<p class="font-serif my-1"><code>if (x == 0) {y++;}</code></p>
<p class="font-serif my-1"><code>if (x == 0) {y++; j = j + y;}</code></p>
<p class="font-serif my-1"><code>if (expr) statement1 else statement2</code></p>
<ul class="list-disc font-serif">
<li class="ml-8">switch case</li>
<li class="ml-8">while: <code>while (expr) statement</code></li>
<li class="ml-8">for: <code>for (initialize; check; update) statement</code></li>
</ul>
</li>
</ul>
<p class="font-serif my-1"><a
href="https://godbolt.org/z/j8s5TEb7a">https://godbolt.org/z/j8s5TEb7a</a></p>
</div>
</section>
<section>
<div>
<h2 id="_1" class="text-xl mt-2 pb-2 font-sans">函数</h2>
<ul class="list-disc font-serif">
<li class="ml-8">在编程中，函数是一段可重复使用的代码块，用于执行特定的任务或完成特定的操作。函数可以接受输入参数，并且可以返回一个值或执行一些操作</li>
<li class="ml-8">代码重用</li>
<li class="ml-8">提高代码可读性</li>
<li class="ml-8">提高代码可测试性（单元测试）</li>
<li class="ml-8">抽象</li>
</ul>
<p class="font-serif my-1"><a
href="https://godbolt.org/z/11bxvT8Ga">https://godbolt.org/z/11bxvT8Ga</a></p>
</div>
</section>
<section>
<div>
<h2 id="_1" class="text-xl mt-2 pb-2 font-sans">数组</h2>
<ul class="list-disc font-serif">
<li class="ml-8">数组就是一整块变量的集合，数组名是数组存放的地址，使用索引确定每个元素的位置</li>
<li class="ml-8">定义：unsigned char temp[10] = {0x11,0x12,0x13};</li>
<li class="ml-8">使用：printf(“%02x ”,temp[0]);</li>
</ul>
<p class="font-serif my-1"><a
href="https://godbolt.org/z/rzo6o1bsE">https://godbolt.org/z/rzo6o1bsE</a></p>
<div class="codehilite">
<pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="cp">#include</span><span class="w"> </span><span class="cpf">&lt;stdio.h&gt;</span>
<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">(){</span>
<span class="w"> </span><span class="kt">unsigned</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="n">temp</span><span class="p">[</span><span class="mi">10</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="mh">0x11</span><span class="p">,</span><span class="mh">0x15</span><span class="p">,</span><span class="mh">0x22</span><span class="p">};</span>
<span class="w"> </span><span class="n">printf</span><span class="p">(</span><span class="s">"temp address: %p</span><span class="se">\n</span><span class="s">"</span><span class="p">,</span><span class="n">temp</span><span class="p">);</span>
@ -228,141 +319,253 @@
<span class="w"> </span><span class="n">printf</span><span class="p">(</span><span class="s">"</span><span class="se">\n</span><span class="s">"</span><span class="p">);</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span>
<span class="p">}</span>
</code></pre></div></div></section><section><div><h2 id="_1" class="text-xl mt-2 pb-2 font-sans">字符串</h2>
<ul class="list-disc font-serif">
<li class="ml-8">字符串是一种特殊的数组，以<code>'\0'</code>结束。</li>
<li class="ml-8">使用 <code>&lt;string.h&gt;</code> 标准库进行更多操作。</li>
</ul>
<p class="font-serif my-1"><a href="https://godbolt.org/z/3jrrvchE1">https://godbolt.org/z/3jrrvchE1</a>
<img alt="static" src="./static/img/ace07efc8ff64ccfa8619a88f51b47d7.png"/></p></div></section><section><div><h2 id="_1" class="text-xl mt-2 pb-2 font-sans">字符串</h2>
<ul class="list-disc font-serif">
<li class="ml-8">使用 <code>&lt;string.h&gt;</code> 标准库进行更多操作。</li>
</ul>
<p class="font-serif my-1"><a href="https://godbolt.org/z/Yrj3dfxKx">https://godbolt.org/z/Yrj3dfxKx</a>
<img alt="static" src="./static/img/853203fa7f4948f18d30f0d4f2586165.png"/></p></div></section><section><div><h2 id="_1" class="text-xl mt-2 pb-2 font-sans">宏定义</h2>
<ul class="list-disc font-serif">
<li class="ml-8"><code>#define</code> 是文本替换，比如 <code>#define MAX 1000</code></li>
<li class="ml-8">C预处理器先处理源文件，替换宏并包含文件。</li>
</ul>
<p class="font-serif my-1"><img alt="static" src="./static/img/f9a01408398844e9b4a0538adaf6c7ca.png"/></p>
<p class="font-serif my-1"><a href="https://godbolt.org/z/aMPxbrMbs">https://godbolt.org/z/aMPxbrMbs</a></p>
<p class="font-serif my-1">gcc -o test test.c -save-temps</p>
<p class="font-serif my-1">关于这块，比较好玩的就是微软早期路径长度在编写时使用了宏定义
<code>#define MAX_PATH 260</code>
导致最长路径除了”C:\”之外，只能有255个字符来指代路径了，虽然现在支持在注册表里面进行更改，不过会引发一些神奇的小bug，这个就留给大家进行探索了</p></div></section><section><div><h2 id="_1" class="text-xl mt-2 pb-2 font-sans">预处理</h2>
<p class="font-serif my-1">C 源文件在编译器看到代码之前首先经过预处理器 CPP
CPP 用单个空格替换注释
CPP 命令以“#”开头
- #include "file.h" /<em> 将 file.h 插入到文件 </em>/
- #include <stdio.h> /<em> 在标准位置查找文件，但没有实际区别 </em>/
- #define PI (3.14159) /<em> 定义常量 </em>/
- #if/#endif /<em> 有条件地包含文本 </em>/</stdio.h></p>
<p class="font-serif my-1">使用 gcc 的 –save-temps 选项查看预处理结果
完整文档位于：http:// /gcc.gnu.org/onlinedocs/cpp/</p></div></section><section><div><h2 id="cat-break" class="text-xl mt-2 pb-2 font-sans">Cat Break!</h2>
<p class="font-serif my-1"><img alt="static" src="./static/img/11693378e53e45449de8116f8ea226bf.png"/></p></div></section></section><section><section><div><h2 id="agenda-part-2" class="text-xl mt-2 pb-2 font-sans">Agenda Part 2</h2>
<p class="font-serif my-1"><img class="float-right" src="./static/img/f5d9dbb8e76c4082b7e17bb8ac138338.png" width=""/></p>
<ul class="list-disc font-serif">
<li class="ml-8">内存与变量</li>
<li class="ml-8">多维数组</li>
<li class="ml-8">指针的初步介绍</li>
<li class="ml-8">指针的进一步理解</li>
<li class="ml-8">指针与数组</li>
<li class="ml-8">指针与const</li>
<li class="ml-8">void指针</li>
<li class="ml-8">警惕UB</li>
</ul></div></section><section><div><h2 id="_1" class="text-xl mt-2 pb-2 font-sans">内存</h2>
<p class="font-serif my-1"><img alt="static" src="./static/img/8334e94e81644ed1a3bdb9a75ceed930.png"/></p></div></section><section><div><h2 id="_1" class="text-xl mt-2 pb-2 font-sans">变量与垃圾值</h2>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">unsigned</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span>
</code></pre>
</div>
</div>
</section>
<section>
<div>
<h2 id="_1" class="text-xl mt-2 pb-2 font-sans">字符串</h2>
<ul class="list-disc font-serif">
<li class="ml-8">字符串是一种特殊的数组，以<code>'\0'</code>结束。</li>
<li class="ml-8">使用 <code>&lt;string.h&gt;</code> 标准库进行更多操作。</li>
</ul>
<p class="font-serif my-1"><a
href="https://godbolt.org/z/3jrrvchE1">https://godbolt.org/z/3jrrvchE1</a></p>
<div class="codehilite">
<pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="cp">#include</span><span class="w"> </span><span class="cpf">&lt;stdio.h&gt;</span>
<span class="cp">#include</span><span class="w"> </span><span class="cpf">&lt;string.h&gt;</span>
<span class="c1">// 字符串以\0结尾</span>
<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">(){</span>
<span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="n">str1</span><span class="p">[]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">"I Can Eat Glass"</span><span class="p">;</span>
<span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="n">str2</span><span class="p">[</span><span class="mi">20</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">"I Can Eat Glass"</span><span class="p">;</span>
<span class="w"> </span><span class="n">printf</span><span class="p">(</span><span class="s">"str1:%s</span><span class="se">\n</span><span class="s">size:%lu</span><span class="se">\n</span><span class="s">str2:%s</span><span class="se">\n</span><span class="s">size:%lu</span><span class="se">\n</span><span class="s">"</span><span class="p">,</span>\
<span class="w"> </span><span class="n">str1</span><span class="p">,</span><span class="n">strlen</span><span class="p">(</span><span class="n">str1</span><span class="p">),</span><span class="n">str2</span><span class="p">,</span><span class="n">strlen</span><span class="p">(</span><span class="n">str2</span><span class="p">));</span>
<span class="p">}</span>
</code></pre>
</div>
<p class="font-serif my-1">使用<code>sizeof</code>和<code>strlen</code>都能获取字符串长度,它们有什么区别呢?</p>
</div>
</section>
<section>
<div>
<h2 id="_1" class="text-xl mt-2 pb-2 font-sans">字符串</h2>
<ul class="list-disc font-serif">
<li class="ml-8">使用 <code>&lt;string.h&gt;</code> 标准库进行更多操作。</li>
</ul>
<p class="font-serif my-1"><a
href="https://godbolt.org/z/sz8Ms1nTj">https://godbolt.org/z/sz8Ms1nTj</a></p>
</div>
</section>
<section>
<div>
<h2 id="_1" class="text-xl mt-2 pb-2 font-sans">宏定义</h2>
<ul class="list-disc font-serif">
<li class="ml-8"><code>#define</code> 是文本替换，比如 <code>#define MAX 1000</code></li>
<li class="ml-8">C预处理器先处理源文件，替换宏并包含文件。</li>
</ul>
<p class="font-serif my-1"><img alt="static"
src="./static/img/3e722aa87b43462fa5629d7d5b542743.png" /></p>
<p class="font-serif my-1"><a
href="https://godbolt.org/z/aMPxbrMbs">https://godbolt.org/z/aMPxbrMbs</a></p>
<p class="font-serif my-1">gcc -o test test.c -save-temps</p>
<p class="font-serif my-1">关于这块，比较好玩的就是微软早期路径长度在编写时使用了宏定义
<code>#define MAX_PATH 260</code>
导致最长路径除了”C:\”之外，只能有255个字符来指代路径了，虽然现在支持在注册表里面进行更改，不过会引发一些神奇的小bug，这个就留给大家进行探索了
</p>
</div>
</section>
<section>
<div>
<h2 id="_1" class="text-xl mt-2 pb-2 font-sans">预处理</h2>
<p class="font-serif my-1">C 源文件在编译器看到代码之前首先经过预处理器 CPP
CPP 用单个空格替换注释
CPP 命令以“#”开头
- #include "file.h" /<em> 将 file.h 插入到文件 </em>/
- #include <stdio.h> /<em> 在标准位置查找文件，但没有实际区别 </em>/
- #define PI (3.14159) /<em> 定义常量 </em>/
- #if/#endif /<em> 有条件地包含文本 </em>/</stdio.h>
</p>
<p class="font-serif my-1">使用 gcc 的 –save-temps 选项查看预处理结果
完整文档位于：http:// /gcc.gnu.org/onlinedocs/cpp/</p>
</div>
</section>
<section>
<div>
<h2 id="cat-break" class="text-xl mt-2 pb-2 font-sans">Cat Break!</h2>
<p class="font-serif my-1"><img alt="static"
src="./static/img/ff8bee4432db4457af8cb7accf38a3c8.png" /></p>
</div>
</section>
</section>
<section>
<section>
<div>
<h2 id="agenda-part-2" class="text-xl mt-2 pb-2 font-sans">Agenda Part 2</h2>
<p class="font-serif my-1"><img class="float-right"
src="./static/img/d77fc3c248284ce88073e56b5498914f.png" width="" /></p>
<ul class="list-disc font-serif">
<li class="ml-8">内存与变量</li>
<li class="ml-8">多维数组</li>
<li class="ml-8">指针的初步介绍</li>
<li class="ml-8">指针的进一步理解</li>
<li class="ml-8">指针与数组</li>
<li class="ml-8">指针与const</li>
<li class="ml-8">void指针</li>
<li class="ml-8">警惕UB</li>
</ul>
</div>
</section>
<section>
<div>
<h2 id="_1" class="text-xl mt-2 pb-2 font-sans">内存</h2>
<p class="font-serif my-1"><img alt="static"
src="./static/img/f9b5785898c74ccb93861c27c0dd6460.png" /></p>
</div>
</section>
<section>
<div>
<h2 id="_1" class="text-xl mt-2 pb-2 font-sans">变量与垃圾值</h2>
<div class="codehilite">
<pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">unsigned</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span>
<span class="kt">int</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">-1</span><span class="p">;</span>
<span class="kt">float</span><span class="w"> </span><span class="n">c</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">1.5f</span><span class="p">;</span>
</code></pre></div>
</code></pre>
</div>
<p class="font-serif my-1">变量可以被分为四个部分：
int ：类型
b ：标识
-1 ：值
&amp;b ：地址</p>
<p class="font-serif my-1"><a href="https://godbolt.org/z/ocbrj7s85">https://godbolt.org/z/ocbrj7s85</a>
<img alt="static" src="./static/img/99aca2ebff314be7a91decceb33ec5c3.png"/></p></div></section><section><div><h2 id="_1" class="text-xl mt-2 pb-2 font-sans">数组的越界行为</h2>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">int</span><span class="w"> </span><span class="n">array</span><span class="p">[</span><span class="mi">5</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="p">};</span>
</code></pre></div>
<p class="font-serif my-1">变量可以被分为四个部分：
int ：类型
b ：标识
-1 ：值
&amp;b ：地址</p>
<p class="font-serif my-1"><a
href="https://godbolt.org/z/ocbrj7s85">https://godbolt.org/z/ocbrj7s85</a>
<img alt="static" src="./static/img/aa1e8bce43c640a3bb4c63867e2f68a0.png" />
</p>
</div>
</section>
<section>
<div>
<h2 id="_1" class="text-xl mt-2 pb-2 font-sans">数组的越界行为</h2>
<div class="codehilite">
<pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">int</span><span class="w"> </span><span class="n">array</span><span class="p">[</span><span class="mi">5</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="w"> </span><span class="p">};</span>
</code></pre>
</div>
<p class="font-serif my-1">array 这个标识符是什么呢？</p>
<p class="font-serif my-1"><img alt="array2" src="./static/img/5f2242615f2b47218fcb51f6fca11a7c.png"/></p>
<p class="font-serif my-1">问：能不能访问array[5]呢？</p></div></section><section><div><h2 id="_1" class="text-xl mt-2 pb-2 font-sans">多维数组</h2>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">int</span><span class="w"> </span><span class="n">array</span><span class="p">[</span><span class="mi">2</span><span class="p">][</span><span class="mi">2</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">},{</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">}};</span>
</code></pre></div>
<p class="font-serif my-1">array 这个标识符是什么呢？</p>
<p class="font-serif my-1"><img alt="array2"
src="./static/img/2325487fe87c4df293bbfbe7986d8fe9.png" /></p>
<p class="font-serif my-1">问：能不能访问array[5]呢？</p>
</div>
</section>
<section>
<div>
<h2 id="_1" class="text-xl mt-2 pb-2 font-sans">多维数组(目前了解即可)</h2>
<div class="codehilite">
<pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">int</span><span class="w"> </span><span class="n">array</span><span class="p">[</span><span class="mi">2</span><span class="p">][</span><span class="mi">2</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">},{</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">}};</span>
</code></pre>
</div>
<p class="font-serif my-1">matrix的类型: int[2][2]
sizeof matrix = sizeof(int) * 2 * 2</p>
<p class="font-serif my-1"><a href="https://godbolt.org/z/Mbq513KnG">https://godbolt.org/z/Mbq513KnG</a></p>
<p class="font-serif my-1"><img alt="2dmatrix" src="./static/img/56425f4f2fc74c3bb8bd7dbb8f049212.png"/></p>
<p class="font-serif my-1">问：下面哪种写法是正确的?</p>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">int</span><span class="w"> </span><span class="n">matrix</span><span class="p">[][</span><span class="mi">2</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">};</span>
<p class="font-serif my-1">matrix的类型: int[2][2]
sizeof matrix = sizeof(int) * 2 * 2</p>
<p class="font-serif my-1"><a
href="https://godbolt.org/z/Mbq513KnG">https://godbolt.org/z/Mbq513KnG</a></p>
<p class="font-serif my-1"><img alt="2dmatrix"
src="./static/img/12462e9d74c8489bb110338d748228c6.png" /></p>
<p class="font-serif my-1">(问：下面哪种写法是正确的?)</p>
<div class="codehilite">
<pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">int</span><span class="w"> </span><span class="n">matrix</span><span class="p">[][</span><span class="mi">2</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">};</span>
<span class="kt">int</span><span class="w"> </span><span class="n">matrix</span><span class="p">[</span><span class="mi">2</span><span class="p">][]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">};</span>
</code></pre></div></div></section><section><div><h2 id="_1" class="text-xl mt-2 pb-2 font-sans">指针</h2>
<p class="font-serif my-1">指针也可以看作一个变量，我们对其的定义是这样的</p>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span>
</code></pre>
</div>
</div>
</section>
<section>
<div>
<h2 id="_1" class="text-xl mt-2 pb-2 font-sans">指针</h2>
<p class="font-serif my-1">指针也可以看作一个变量，我们对其的定义是这样的</p>
<div class="codehilite">
<pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span>
<span class="kt">int</span><span class="o">*</span><span class="w"> </span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">&amp;</span><span class="n">a</span><span class="p">;</span>
</code></pre></div>
</code></pre>
</div>
<p class="font-serif my-1">int<em> : int表示指针指向的元素类型 </em>代表的是我要定义一个指针
p : 标识符
&amp;a : 指针的值（指针指向的地址）
&amp;p : 存放指针的地址</p>
<p class="font-serif my-1"><img alt="static" src="./static/img/bf0df0ad37274bcda7c846a9574124f0.png"/></p></div></section><section><div><h2 id="_1" class="text-xl mt-2 pb-2 font-sans">指针初始化与使用</h2>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">int</span><span class="o">*</span><span class="w"> </span><span class="n">p</span><span class="p">;</span>
<p class="font-serif my-1">int<em> : int表示指针指向的元素类型 </em>代表的是我要定义一个指针
p : 标识符
&amp;a : 指针的值（指针指向的地址）
&amp;p : 存放指针的地址</p>
<p class="font-serif my-1"><img alt="static"
src="./static/img/276ea65bb0824b8ab636b2eaea91d478.png" /></p>
</div>
</section>
<section>
<div>
<h2 id="_1" class="text-xl mt-2 pb-2 font-sans">指针初始化与使用</h2>
<div class="codehilite">
<pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">int</span><span class="o">*</span><span class="w"> </span><span class="n">p</span><span class="p">;</span>
<span class="o">*</span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w"> </span><span class="c1">// 危险，p是野指针</span>
</code></pre></div>
</code></pre>
</div>
<p class="font-serif my-1">应该这么做</p>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">int</span><span class="o">*</span><span class="w"> </span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">NULL</span><span class="p">;</span>
</code></pre></div>
<p class="font-serif my-1">应该这么做</p>
<div class="codehilite">
<pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">int</span><span class="o">*</span><span class="w"> </span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">NULL</span><span class="p">;</span>
</code></pre>
</div>
<p class="font-serif my-1">当要使用指针指向的值的时候，可以对指针进行解引用</p>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span>
<p class="font-serif my-1">当要使用指针指向的值的时候，可以对指针进行解引用</p>
<div class="codehilite">
<pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span>
<span class="kt">int</span><span class="o">*</span><span class="w"> </span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">&amp;</span><span class="n">a</span><span class="p">;</span>
<span class="o">*</span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span>
<span class="n">printf</span><span class="p">(</span><span class="s">"%d"</span><span class="p">,</span><span class="o">*</span><span class="n">p</span><span class="p">);</span>
</code></pre></div></div></section><section><div><h2 id="_1" class="text-xl mt-2 pb-2 font-sans">指针的作用</h2>
<p class="font-serif my-1">指针是C语言的精髓，广泛运用于传参等方面</p>
<p class="font-serif my-1"><a href="https://godbolt.org/z/8MeTzaGjo">https://godbolt.org/z/8MeTzaGjo</a></p>
<p class="font-serif my-1">看完这个例子后，想一想scanf("%d",&amp;a);为什么需要取a的地址？</p></div></section><section><div><h2 id="_1" class="text-xl mt-2 pb-2 font-sans">指针数组和数组指针</h2>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">int</span><span class="w"> </span><span class="o">*</span><span class="n">p</span><span class="p">[</span><span class="mi">10</span><span class="p">];</span>
<span class="kt">int</span><span class="w"> </span><span class="p">(</span><span class="o">*</span><span class="n">p</span><span class="p">)[</span><span class="mi">10</span><span class="p">];</span>
<span class="c1">// []运算符的优先级&gt;*运算符的优先级</span>
</code></pre></div>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">int</span><span class="w"> </span><span class="o">*</span><span class="n">p</span><span class="p">[</span><span class="mi">10</span><span class="p">];</span>
<span class="c1">// 化为int* array[] -&gt; 存放着 10个指向int类型的指针 的数组</span>
<span class="kt">int</span><span class="w"> </span><span class="p">(</span><span class="o">*</span><span class="n">p</span><span class="p">)[</span><span class="mi">10</span><span class="p">];</span>
<span class="c1">// 化为int pointer[] -&gt; 指向 存放了10个int类型的数组 的指针</span>
</code></pre></div></div></section><section><div><h2 id="_1" class="text-xl mt-2 pb-2 font-sans">加大难度</h2>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">int</span><span class="o">*</span><span class="w"> </span><span class="p">(</span><span class="o">*</span><span class="n">p</span><span class="p">)[</span><span class="mi">20</span><span class="p">][</span><span class="mi">10</span><span class="p">];</span>
</code></pre></div>
<p class="font-serif my-1">问：p是什么？
p是指针还是数组？
p的类型是什么？</p>
<p class="font-serif my-1">想明白之后点击链接查看答案
<a href="https://godbolt.org/z/hv6rnTj5Y">https://godbolt.org/z/hv6rnTj5Y</a></p></div></section><section><div><h2 id="_1" class="text-xl mt-2 pb-2 font-sans">数组和指针的关系</h2>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="c1">// p1的类型是int* , array的类型是int[10]</span>
</code></pre>
</div>
</div>
</section>
<section>
<div>
<h2 id="_1" class="text-xl mt-2 pb-2 font-sans">指针的作用</h2>
<p class="font-serif my-1">指针是C语言的精髓，广泛运用于传参等方面</p>
<p class="font-serif my-1"><a
href="https://godbolt.org/z/8MeTzaGjo">https://godbolt.org/z/8MeTzaGjo</a></p>
<p class="font-serif my-1">看完这个例子后，想一想scanf("%d",&amp;a);为什么需要取a的地址？</p>
</div>
</section>
<section>
<div>
<h2 id="_1" class="text-xl mt-2 pb-2 font-sans">数组和指针的关系</h2>
<div class="codehilite">
<pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="c1">// p1的类型是int* , array的类型是int[10]</span>
<span class="kt">int</span><span class="w"> </span><span class="n">array</span><span class="p">[</span><span class="mi">10</span><span class="p">];</span>
<span class="kt">int</span><span class="w"> </span><span class="o">*</span><span class="n">p1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">array</span><span class="p">;</span>
<span class="c1">// p2的类型是int*[2] , matrix的类型是int[][]</span>
<span class="kt">int</span><span class="w"> </span><span class="n">matrix</span><span class="p">[</span><span class="mi">2</span><span class="p">][</span><span class="mi">2</span><span class="p">];</span>
<span class="kt">int</span><span class="w"> </span><span class="p">(</span><span class="o">*</span><span class="n">p2</span><span class="p">)[</span><span class="mi">2</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">matrix</span><span class="p">;</span>
</code></pre></div>
</code></pre>
</div>
<p class="font-serif my-1">数组与其元素类型的指针存在隐式转换，指向数组首元素的指针可通过数组类型表达式初始化。</p>
<p class="font-serif my-1">问：二维数组可以和二维指针相互转化吗</p>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">int</span><span class="w"> </span><span class="n">array</span><span class="p">[</span><span class="mi">2</span><span class="p">][</span><span class="mi">2</span><span class="p">];</span>
<p class="font-serif my-1">数组与其元素类型的指针存在隐式转换，指向数组首元素的指针可通过数组类型表达式初始化。</p>
<p class="font-serif my-1">问：二维数组可以和二维指针相互转化吗</p>
<div class="codehilite">
<pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">int</span><span class="w"> </span><span class="n">array</span><span class="p">[</span><span class="mi">2</span><span class="p">][</span><span class="mi">2</span><span class="p">];</span>
<span class="kt">int</span><span class="o">**</span><span class="w"> </span><span class="n">ptr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">array</span><span class="p">;</span>
<span class="c1">//可以这么做吗</span>
</code></pre></div></div></section><section><div><h2 id="const" class="text-xl mt-2 pb-2 font-sans">const与指针的关系</h2>
<p class="font-serif my-1">前文提到const就像一把锁，被它锁到的事物不能被更改</p>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="p">;</span>
</code></pre>
</div>
</div>
</section>
<section>
<div>
<h2 id="const" class="text-xl mt-2 pb-2 font-sans">const与指针的关系</h2>
<p class="font-serif my-1">前文提到const就像一把锁，被它锁到的事物不能被更改</p>
<div class="codehilite">
<pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="p">;</span>
<span class="c1">// 锁住指针p指向的int类型变量</span>
<span class="k">const</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="o">*</span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">&amp;</span><span class="n">a</span><span class="p">;</span>
@ -370,36 +573,61 @@ p的类型是什么？</p>
<span class="kt">int</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="o">*</span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">&amp;</span><span class="n">a</span><span class="p">;</span>
<span class="c1">// 一起锁</span>
<span class="k">const</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="o">*</span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">&amp;</span><span class="n">a</span><span class="p">;</span>
</code></pre></div>
</code></pre>
</div>
<p class="font-serif my-1">假设你有一段音频文件，你想要进行播放，那你绝对不想播放器修改你的音频，那你可以使用const来设计函数，这样就绝对无法更改了</p>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">void</span><span class="w"> </span><span class="nf">wav_player</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="o">*</span><span class="n">ptr</span><span class="p">);</span>
</code></pre></div></div></section><section><div><h2 id="_1" class="text-xl mt-2 pb-2 font-sans">指针的加减法</h2>
<p class="font-serif my-1">加、减
加、减整数n -&gt; 指向后/前第n个元素</p>
<p class="font-serif my-1">指针相减
表示指针之间的偏移量</p>
<p class="font-serif my-1">仅当原指针和结果指针都指向同一数组中的元素，或该数组的尾后一位置，行为才有定义。</p>
<p class="font-serif my-1"><a href="https://godbolt.org/z/q9M6W81x3">https://godbolt.org/z/q9M6W81x3</a></p></div></section><section><div><h2 id="void" class="text-xl mt-2 pb-2 font-sans">void*</h2>
<p class="font-serif my-1">使用void类型指针的时候无法进行解引用，也无法进行加减运算
使用void*类型的指针的时候一定要对其进行强制类型转化</p>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span>
<span class="kt">void</span><span class="w"> </span><span class="o">*</span><span class="n">p</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">&amp;</span><span class="n">a</span><span class="p">;</span>
<span class="n">printf</span><span class="p">(</span><span class="s">"%d</span><span class="se">\n</span><span class="s">"</span><span class="p">,</span><span class="o">*</span><span class="p">((</span><span class="kt">int</span><span class="o">*</span><span class="p">)</span><span class="n">p</span><span class="p">));</span>
</code></pre></div></div></section><section><div><h2 id="ub" class="text-xl mt-2 pb-2 font-sans">警惕UB(未定义行为)</h2>
<p class="font-serif my-1">我们很多时候需要警惕未定义行为，就比如说</p>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="n">a</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">++</span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="mi">1</span><span class="p">;</span>
</code></pre></div>
<p class="font-serif my-1">假设你有一段音频文件，你想要进行播放，那你绝对不想播放器修改你的音频，那你可以使用const来设计函数，这样就绝对无法更改了</p>
<div class="codehilite">
<pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="kt">void</span><span class="w"> </span><span class="nf">wav_player</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="o">*</span><span class="n">ptr</span><span class="p">);</span>
</code></pre>
</div>
</div>
</section>
<section>
<div>
<h2 id="_1" class="text-xl mt-2 pb-2 font-sans">指针的加减法</h2>
<p class="font-serif my-1">加、减
加、减整数n -&gt; 指向后/前第n个元素</p>
<p class="font-serif my-1">指针相减
表示指针之间的偏移量</p>
<p class="font-serif my-1">仅当原指针和结果指针都指向同一数组中的元素，或该数组的尾后一位置，行为才有定义。</p>
<p class="font-serif my-1"><a
href="https://godbolt.org/z/q9M6W81x3">https://godbolt.org/z/q9M6W81x3</a></p>
</div>
</section>
<section>
<div>
<h2 id="ub" class="text-xl mt-2 pb-2 font-sans">警惕UB(未定义行为)</h2>
<p class="font-serif my-1">我们很多时候需要警惕未定义行为，就比如说</p>
<div class="codehilite">
<pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="n">a</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">++</span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="mi">1</span><span class="p">;</span>
</code></pre>
</div>
<p class="font-serif my-1">i在这里多次使用且数值发生了改变，没人知道a[i]先执行还是++i先执行</p>
<p class="font-serif my-1">还有就是</p>
<div class="codehilite"><pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="c1">// i=0</span>
<p class="font-serif my-1">i在这里多次使用且数值发生了改变，没人知道a[i]先执行还是++i先执行</p>
<div class="codehilite">
<pre class="bg-gray-100 overflow-x-auto rounded p-2 mb-2 mt-2"><span/><code><span class="c1">// i=0</span>
<span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">f</span><span class="p">(</span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="o">+</span><span class="n">f</span><span class="p">(</span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="o">-</span><span class="n">f</span><span class="p">(</span><span class="n">i</span><span class="o">++</span><span class="p">);</span>
</code></pre></div>
</code></pre>
</div>
<p class="font-serif my-1">虽然在最后的结果上编译器会将其翻译为int a = (f(i++)+f(i++))-f(i++);
但没人知道哪个f(i++)最先执行，可能是第一个，也可能是第三个</p></div></section><section><div><h2 id="ask-time" class="text-xl mt-2 pb-2 font-sans">Ask Time</h2>
<p class="font-serif my-1"><img alt="static" src="./static/img/cdfa9e87117d4baf82ca4e2f5de0b837.png"/></p></div></section></section>
<p class="font-serif my-1">虽然在最后的结果上编译器会将其翻译为int a = (f(i++)+f(i++))-f(i++);
但没人知道哪个f(i++)最先执行，可能是第一个，也可能是第三个</p>
<blockquote>
<p class="font-serif my-1">详情请参考
https://zh.cppreference.com/w/c/language/behavior
https://zh.cppreference.com/w/c/language/eval_order</p>
</blockquote>
</div>
</section>
<section>
<div>
<h2 id="ask-time" class="text-xl mt-2 pb-2 font-sans">Ask Time</h2>
<p class="font-serif my-1"><img alt="static"
src="./static/img/d2218f607d3a4237973e1fbd7506fb67.png" /></p>
</div>
</section>
</section>
</div>
</div>

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69
Others/Codes/Lecture2/1-control-flow.c
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@ -1,69 +0,0 @@
#include <stdio.h>
// C中的控制流
int main(int argc,char* argv[]){
// 条件分支
// if else
if(argc == 1){
printf("args = NULL\n");
}else if(argc == 2){
printf("args = %d\n",argc-1);
printf("argv:%s\n",argv[1]);
}else{
printf("args = %d\n",argc-1);
}
printf("\n");
//switch
switch (argc)
{
case 1:
printf("args = NULL\n");
break;
case 2:
printf("args = %d\n",argc-1);
printf("argv:%s\n",argv[1]);
break;
default:
printf("args = %d\n",argc-1);
break;
}
// 三元表达式
argc == 2? printf("yes\n\n") : printf("no\n\n");
// 循环结构
int i=10;
while(i!=0){
printf("%d ",i);
i--;
}printf("\n");
do{
printf("%d ",i);
i++;
}while(i<10);
printf("\n");
for(i=0;i<10;i++){
printf("%d ",i);
}printf("\n\n");
// 跳转控制语句
/**
* @param break 跳出循环或者是跳出switch语句
* @param continue 跳过下面的步骤重新开始下一次循环
*/
printf("goto语句示范:\n");
int go = 0;
lable:
printf("%d ",go);
if(go < 3){
go++;
goto lable;
}
printf("\n");
}

20
Others/Codes/Lecture2/2-function.c
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@ -1,20 +0,0 @@
#include <stdio.h>
// 函数声明
int fact(int);
int main(){
printf("%d",fact(5));
}
// 函数定义
int fact(int n){
if (n<=1){
return 1;
}
int sum=1,i;
for(i=1;i<=n;i++){
sum*=i;
}
return sum;
}

19
Others/Codes/Lecture2/3-array.c
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@ -1,19 +0,0 @@
#include <stdio.h>
int main(){
// 定义
unsigned char temp[10] = {0x11,0x15,0x22};
// 数组的地址
printf("temp address: %p\n",temp);
// 更改
temp[3] = 0xa8;
// 使用
for (size_t i=0;i<10;i++){
printf("%02x ",temp[i]);
}
printf("\n");
return 0;
}

12
Others/Codes/Lecture2/4-string.c
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@ -1,12 +0,0 @@
#include <stdio.h>
#include <string.h>
// 字符串以\0结尾
int main(){
char str1[] = "I Can Eat Glass";
char str2[20] = "I Can Eat Glass";
printf("str1:%s\nsize:%lu\nstr2:%s\nsize:%lu\n",\
str1,strlen(str1),str2,strlen(str2));
}

32
Others/Codes/Lecture2/5-string-advance.c
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@ -1,32 +0,0 @@
#include <stdio.h>
#include <string.h>
// string.h标准库的几个常用函数
int main(){
char str1[] = "I Can Eat Glass";
char str2[] = "我能吞下玻璃而不伤身体";
printf("str1:%s\nsize:%lu\nstr2:%s\nsize:%lu\n",\
str1,strlen(str1),str2,strlen(str2));
// 字符串比较
int h = strcmp(str1,str2);
if(h!=0){
if(h>0){
printf("str1更大\n");
}
else{
printf("str2更大\n");
}
}
else{
printf("str1和str2一样大\n");
}
// 字符串赋值
strcpy(str1,"I love windows\n");
printf("str1:%s",str1);
return 0;
}

10
Others/Codes/Lecture2/6-macro.c
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@ -1,10 +0,0 @@
#include <stdio.h>
#define MAX 1000
int main(int argc,char* argv[])
{
printf("MAX: %d",MAX);
return 0;
}

13
Others/Codes/Lecture2/7-variable.c
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@ -1,13 +0,0 @@
#include <stdio.h>
int main(){
unsigned int a;
int b;
float c;
printf("a,b,c各元素的值\n");
printf("%u %d %f\n",a,b,c);
printf("a,b,c各元素的地址\n");
printf("%p %p %p\n",&a,&b,&c);
return 0;
}

10
Others/Codes/Lecture2/8-nested-array
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@ -1,10 +0,0 @@
#include <stdio.h>
int main(void) {
int matrix[2][2] = { {1, 2}, {3, 4} };
printf("%p %p %p %p\n", &matrix[0][0], &matrix[0][1], &matrix[1][0], &matrix[1][1]);
printf("sizeof matrix: %d\n", sizeof matrix);
printf("sizeof matrix[0]: %d\n", sizeof matrix[0]);
printf("sizeof matrix[1]: %d\n", sizeof matrix[1]);
return 0;
}

23
Others/Codes/Lecture2/9-pointer.c
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@ -1,23 +0,0 @@
#include <stdio.h>
void swap1(int x, int y) {
int t = x;
x = y;
y = t;
}
void swap2(int *x, int *y) {
int t = *x;
*x = *y;
*y = t;
}
int main(void) {
int a = 1, b = 2;
printf("a = %d, b = %d\n", a, b);
swap1(a, b);
printf("a = %d, b = %d after swap1\n", a, b);
swap2(&a, &b);
printf("a = %d, b = %d after swap2\n", a, b);
return 0;
}

7
Others/Codes/Lecture2/A-pointer-puzzle.c
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@ -1,7 +0,0 @@
#include <stdio.h>
int main(void) {
// int* (*p)[20][10];
// p是一个指向 存放int*类型的二维数组 的指针
}

14
Others/Codes/Lecture2/B-pointer-clac.c
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@ -1,14 +0,0 @@
#include <stdio.h>
int main(void) {
int array[10] = {0};
printf("array = %p\n", array);
int *p1 = array, *p2 = array;
printf("p1 = %p, p2 = %p\n", p1, p2);
p1 = p1 + 1;
printf("p1 = %p, p2 = %p\n", p1, p2);
p2 = p2 + 9;
printf("p1 = %p, p2 = %p\n", p1, p2);
printf("p2 - p1 = %u\n", (unsigned int)(p2-p1));
return 0;
}

5
Others/Codes/Lecture2/README.md
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@ -1,5 +0,0 @@
> 在本目录下打开终端,输入
```bash
make
```
> 在`./build`目录下生成对应的可执行文件

21
Others/Codes/Lecture2/makefile
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@ -1,21 +0,0 @@
CC = gcc
CFLAGS = -Wall -g
SRC = $(wildcard *.c)
EXE = $(patsubst %.c, ./build/%, $(SRC))
.PHONY: all
all: build_dir $(EXE)
./build/%: %.c
$(CC) $(CFLAGS) -o $@ $<
build_dir:
mkdir -p build
.PHONY: clean
clean:
rm -rf ./build

5
site.sh
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@ -5,9 +5,10 @@ SOURCE=("$WORK_DIR/index.html" "$WORK_DIR/Lectures")
mkdir -p "$SITE_DIR"
cp -r "${SOURCE[@]}" "$SITE_DIR"
CODE_DIR="$WORK_DIR/Others/Codes"
JEKLLY_TOOL_DIR="$WORK_DIR/Tools/ghpages-mini-fileserver"
cp -r "$CODE_DIR" "$JEKLLY_TOOL_DIR/resources"
RESOURCE="$JEKLLY_TOOL_DIR/resources"
mkdir -p "$RESOURCE"
find "$WORK_DIR/Lectures" -type d -name "Codes" -exec cp -r "{}" "$RESOURCE" \;
bash "$JEKLLY_TOOL_DIR/prenodes.sh"
cd "$JEKLLY_TOOL_DIR" && bundle exec jekyll build --baseurl "$1"
cp -r "$JEKLLY_TOOL_DIR/_site" "$SITE_DIR"