Convert given string so that it holds only distinct characters in C++

In this tutorial, we will be discussing a program to convert given string so that it holds only distinct characters.

For this we will be provided with a string. Our task is to traverse through the string and replace all the recurring characters with any random characters that are not already present into the string.

Example

Live Demo

#include<bits/stdc++.h>
using namespace std;
//collecting the distinct characters
//in the string
int calculate_zero(int i, int occurrences[]){
   while (i < 26) {
      //if it is present only once
      if (occurrences[i] == 0)
         return i;
      i++;
   }
   //if all are doubles or more
   return -1;
}
//printing the modified string
string print_modified(string str) {
   int n = str.length();
   //if conversion
   //not possible
   if (n > 26)
      return "-1";
   string ch = str;
   int i, occurrences[26] = {0};
   //counting the occurrences
   for (i = 0; i < n; i++)
      occurrences[ch[i] - 'a']++;
   int index = calculate_zero(0, occurrences);
   for (i = 0; i < n; i++) {
      //replacing the character
      if (occurrences[ch[i] - 'a'] > 1) {
         occurrences[ch[i] - 'a']--;
         ch[i] = (char)('a' + index);
         occurrences[index] = 1;
         //moving to the next character
         index = calculate_zero(index + 1, occurrences);
      }
   }
   cout << ch << endl;
}
int main() {
   string str = "tutorialspoint";
   print_modified(str);
}