#include <iostream>
#include <string>
#include <random>

std::string generateRandomId(size_t length = 0)
{
    static const std::string allowed_chars {"123456789BCDFGHJKLMNPQRSTVWXZbcdfghjklmnpqrstvwxz"};

    static thread_local std::default_random_engine randomEngine(std::random_device{}());
    static thread_local std::uniform_int_distribution<int> randomDistribution(0, allowed_chars.size() - 1);

    std::string id(length ? length : 32, '\0');

    for (std::string::value_type& c : id) {
        c = allowed_chars[randomDistribution(randomEngine)];
    }

    return id;
}

int main()
{
    std::cout << generateRandomId() << std::endl;
}

Mehrdad Afshari的回答可以解决这个问题，但我觉得对于这个简单的任务来说，它有点太啰嗦了。查询表有时可以创造奇迹:

#include <ctime>
#include <iostream>
#include <unistd.h>

std::string gen_random(const int len) {
    static const char alphanum[] =
        "0123456789"
        "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
        "abcdefghijklmnopqrstuvwxyz";
    std::string tmp_s;
    tmp_s.reserve(len);

    for (int i = 0; i < len; ++i) {
        tmp_s += alphanum[rand() % (sizeof(alphanum) - 1)];
    }
    
    return tmp_s;
}

int main(int argc, char *argv[]) {
    srand((unsigned)time(NULL) * getpid());     
    std::cout << gen_random(12) << "\n";        
    return 0;
}

注意rand生成的随机数质量很差。

#include <iostream>
#include <string>
#include <stdlib.h>
int main()
{
    int size;
    std::cout << "Enter size : ";
    std::cin >> size;
    std::string str;
    for (int i = 0; i < size; i++)
    {
        auto d = rand() % 26 + 'a';
        str.push_back(d);
    }
    for (int i = 0; i < size; i++)
    {
        std::cout << str[i] << '\t';
    }

    return 0;
}

这是另一种改编，因为没有一个答案能满足我的需求。

首先，如果rand()用于生成随机数，那么每次运行都将得到相同的输出。随机数生成器的种子必须是某种随机的。

在c++ 11中，你可以包含随机库，并且可以使用random_device和mt19937初始化种子。这个种子将由操作系统提供，它对我们来说足够随机(例如，时钟)。你可以给出一个范围边界(在我的例子中是[0,25])。

我只需要随机字符串小写字母，所以我利用字符加法。“人物池”的方法并不适合我。

#include <random>    
void gen_random(char *s, const int len){
    static std::random_device rd;
    static std::mt19937 mt(rd());
    static std::uniform_int_distribution<int> dist(0, 25);
    for (int i = 0; i < len; ++i) {
        s[i] = 'a' + dist(mt);
    }
    s[len] = 0;
}

//C++ Simple Code
#include <bits/stdc++.h>
using namespace std;
int main() {
vector<char> alphanum =
    {'0','1','2','3','4',
'5','6','7','8','9',
'A','B','C','D','E','F',
'G','H','I','J','K',
'L','M','N','O','P',
'Q','R','S','T','U',
'V','W','X','Y','Z',
'a','b','c','d','e','f',
'g','h','i','j','k',
'l','m','n','o','p',
'q','r','s','t','u',
'v','w','x','y','z'
};
string s="";
int len=5;
srand(time(0)); 
for (int i = 0; i <len; i++) {
    int t=alphanum.size()-1;
    int idx=rand()%t;
    s+= alphanum[idx];
}
cout<<s<<" ";
return 0;
}

一些更简单和更基本的东西，如果你想让你的字符串包含任何可打印的字符:

#include <time.h>   // we'll use time for the seed
#include <string.h> // this is for strcpy

void randomString(int size, char* output) // pass the destination size and the destination itself
{
    srand(time(NULL)); // seed with time

    char src[size];
    size = rand() % size; // this randomises the size (optional)

    src[size] = '\0'; // start with the end of the string...

    // ...and work your way backwards
    while(--size > -1)
        src[size] = (rand() % 94) + 32; // generate a string ranging from the space character to ~ (tilde)

    strcpy(output, src); // store the random string
}