Qt使用示例:

QString random_string(int length=32, QString allow_symbols=QString("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")) {
    QString result;
    qsrand(QTime::currentTime().msec());
    for (int i = 0; i < length; ++i) {            
        result.append(allow_symbols.at(qrand() % (allow_symbols.length())));
    }
    return result;
}

我刚刚测试了这个，它工作得很好，不需要查找表。Rand_alnum()在某种程度上强制输出字母数字，但因为它从可能的256个字符中选择62个，所以这不是什么大问题。

#include <cstdlib>   // for rand()
#include <cctype>    // for isalnum()   
#include <algorithm> // for back_inserter
#include <string>

char 
rand_alnum()
{
    char c;
    while (!std::isalnum(c = static_cast<char>(std::rand())))
        ;
    return c;
}


std::string 
rand_alnum_str (std::string::size_type sz)
{
    std::string s;
    s.reserve  (sz);
    generate_n (std::back_inserter(s), sz, rand_alnum);
    return s;
}

//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;
}

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。

您可以使用random()方法生成一个基本的随机字符串。 下面的代码生成一个由小写字母、大写字母和数字组成的随机字符串。

String randomStrGen(int numChars){
  String genStr="";
  int sizeStr=0;
  
  while(sizeStr<numChars){
    int asciiPos= random(48,122);
    if((asciiPos>57 && asciiPos<65) || (asciiPos>90 && asciiPos<97))
      continue;
    genStr+=(char) asciiPos;
    sizeStr++;
  }
  
  return genStr;
}

如果需要更安全的随机数生成器，只需将random()函数替换为更安全的随机数生成器。

此外，还可以通过将ASCII限制(48,122)更改为另一个自定义值来调整可能生成的字符

void strGetRandomAlphaNum(char *sStr, unsigned int iLen)
{
  char Syms[] = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
  unsigned int Ind = 0;
  srand(time(NULL) + rand());
  while(Ind < iLen)
  {
    sStr[Ind++] = Syms[rand()%62];
  }
  sStr[iLen] = '\0';
}