C++ 隨機生成由大小寫字母和數字組成的字符串

頭文件

#include <time.h>　　//秒

#include <sys/timeb.h> //毫秒

std::string GetRandomStr(int len) {
        //毫秒
        struct timeb time_seed;
        ftime(&time_seed);
        srand(time_seed.time * 1000 + time_seed.millitm);

        //秒
        //srand(time(0));

        std::string random_str("");
        for (int i = 0; i < len; ++i) {
            switch (rand() % 3) {
            case 1:
                random_str += ('A' + rand() % 26);
                break;
            case 2:
                random_str += ('a' + rand() % 26);
                break;
            default:
                random_str += ('0' + rand() % 10);
                break;
            }
        }

        return random_str;
    }