随机生成四位验证码c语言

很高兴为您解答。以下是C语言生成四位验证码的代码示例：

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main()
{
    char checkcode[5] = ""; // 验证码字符串
    int i, current, current1, tmp;
    srand((unsigned)time(NULL)); // 初始化随机数种子

    for (i = 0; i < 4; i++)
    {
        current = rand() % 3; // 生成随机数与循环次数比对
        current1 = rand() % 3;
        if (current == i)
        {
            tmp = rand() % 26 + 65; // 65~90为ASCii码表A~Z
        }
        else if (current1 == i)
        {
            tmp = rand() % 26 + 97; // 97~122为ASCii码表a~z
        }
        else
        {
            tmp = rand() % 10 + 48; // 48~57为ASCii码表0~9
        }
        checkcode[i] = (char)tmp;
    }
    checkcode[4] = '\0'; // 字符串结尾

    printf("验证码为：%s\n", checkcode);

    return 0;
}