add linear regression details

source/_posts/language/C.md

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+---
+title: C lang
+tags: C C++
+abbrlink: 12462
+date: 2025-01-15 20:41:26
+---
+
+### c lang在windows下的开发（VS code）
+[WinLibs - GCC+MinGW-w64 compiler for Windows](https://winlibs.com/#download-release)下载你需要的版本
+解压到`D:\ProgramModule`，并将 `bin\`加入环境变量`PATH`
+打开新的`Terminal`输入`gcc -v`，查看`gcc`是否安装成功
+在`VS code` 的插件管理下载`Code Runner`、`C\C++`这两个插件
+在`*.c`源文件的内容区，右键点击`Run Code` ，即可运行成功
+![](/img/language/c-env-conf.png)
+
+### 数据类型
+- 整数类型
+  ```c
+    short a = 12;
+    int b = 100;
+    long c = 1000L;
+    long long d = 1000000LL;
+    unsigned int e = 10;
+    printf("a: %hd\n",a);
+    printf("b: %d\n",b);
+    printf("c: %ld\n",c);
+    printf("d: %lld\n",d);
+    printf("e: %u\n",e);
+    printf("f: %.3f\n",f);
+    ```
+- 小数类型
+  ```c
+    float f = 3.14F;
+    printf("f: %.3f\n",f);
+    double g = 5.65;
+    printf("g: %.2lf\n",g);
+    ```
+- 字符类型
+  ```c
+    char h = 'x';
+    printf("x: %c\n",x);
+    ```
+### 类型转换
+- 隐式转换
+- 强制转换
+  ```c
+    int b = 23;
+    short c = (short) b;
+    ```
+### 数组
+```c
+#include <stdio.h>
+
+int main(){
+    int arr [10] = {2,3,4,5,6,7,8,9,10,11};
+    arr[0] = 1525;
+    *(arr+1) = 25;
+    int len = sizeof(arr)/sizeof(arr[0]);
+    void printArr(int arr[], int len){
+        for (int i = 0; i < len;i++){
+            printf("%d\t",arr[i]);
+        }
+    }
+    printArr(arr,len);
+    return 0;
+}
+```
+### 指针
+```c
+    // swap the value of a and b
+    void swap(int* x, int* y){
+        int temp = *x;
+        *x = *y;
+        *y = temp;
+
+    }
+    int a = 5;
+    int b = 10;
+    swap(&a, &b);
+    printf("a = %d b = %d\n", a, b);
+```