How do I create a random alpha-numeric string using C++?

C++Server Side ProgrammingProgramming

In this section we will see how to generate a random alphanumeric string using C++. Here we are providing lowercase letters, uppercase letters and numbers (0-9). This program takes the characters randomly, then creates the random string.

Input: Here we are giving the string length
Output: A random string of that length. Example “XSme6VAsvJ”


Step 1:Define array to hold all uppercase, lowercase letters and numbers
Step 2: Take length n from user
Step 3: Randomly choose characters’ n times and create a string of length n
Step 4: End

Example Code

 Live Demo

#include <iostream>
#include <string>
#include <cstdlib>
#include <ctime>
using namespace std;
static const char alphanum[] = "0123456789" "ABCDEFGHIJKLMNOPQRSTUVWXYZ" "abcdefghijklmnopqrstuvwxyz";
int len = sizeof(alphanum) - 1;
char genRandom() { // Random string generator function.
   return alphanum[rand() % len];
int main() {
   int n;
   cout << "Enter string length: ";
   cin >> n;
   for(int z = 0; z < n; z++) {    //generate string of length n
      cout << genRandom(); //get random character from the given list
   return 0;


Enter string length: 10
Published on 28-Mar-2019 13:15:02