C/C++：常用函数

**C/C++ 常用函数**

在 C 和 C++ 编程中，函数是程序的基本组成单位。以下是一些常用的函数，包括数学运算、字符串处理、数组操作等。

### 数学运算函数####1. `abs()`

返回一个数的绝对值。

c#include <stdlib.h>

int abs(int a) {
 return (a >=0) ? a : -a;
}

c#include 

double pow(double base, double exponent) {
 return pow(base, exponent);
}

c#include 

double sqrt(double a) {
 return sqrt(a);
}

c#include <string.h>

void strcpy(char *dest, const char *src) {
 while ((*dest = *src) != '0') {
 dest++;
 src++;
 }
}

c#include <string.h>

char *strcat(char *dest, const char *src) {
 while (*dest != '0') {
 dest++;
 }

 while ((*dest = *src) != '0') {
 src++;
 dest++;
 }

 return dest;
}

c#include <string.h>

int strcmp(const char *s1, const char *s2) {
 while (*s1 == *s2 && *s1 != '0') {
 s1++;
 s2++;
 }

 return *s1 - *s2;
}

c#include <string.h>

void memcpy(void *dest, const void *src, size_t n) {
 char *d = (char *)dest;
 const char *s = (const char *)src;

 for (size_t i =0; i < n; i++) {
 d[i] = s[i];
 }
}

c#include <string.h>

void memset(void *s, int c, size_t n) {
 char *d = (char *)s;

 for (size_t i =0; i < n; i++) {
 d[i] = (char)c;
 }
}

c#include <stdlib.h>

int rand(void) {
 return rand();
}

c#include <stdlib.h>

void srand(unsigned int seed) {
 srand(seed);
}