XOR of Prime Frequencies of Characters in a String in C++

In this problem, we are given a string of characters, our task is to print the XOR of frequencies of characters of the string whose frequency of occurrence is a prime number.

Let’s take an example to understand the problem,

Input − TutorialsPoint

Output −

Here, we will check the frequency of occurrence of each character of the string and then find XOR of all the characters whose frequency is a prime number. For this will create an array of prime frequencies. Then we will store frequencies of characters of a string in a map and then matching with prime frequency array. If a match is found the xor is found, on looping to all elements of the map we can find the required XOR’s.

Example

Program to show the implementation of our solution,

 Live Demo

#include <bits/stdc++.h>
using namespace std;
void findPrimes(bool prime[], int p_size){
   prime[0] = false;
   prime[1] = false;
   for (int p = 2; p * p <= p_size; p++) {
      if (prime[p]) {
         for (int i = p * 2; i <= p_size; i += p)
            prime[i] = false;
      }
   }
}
int findPrimeXOR(string s){
   bool prime[100005];
   memset(prime, true, sizeof(prime));
   findPrimes(prime, 10005);
   int i, j;
   map<char, int> charFreq;
   for (i = 0; i < s.length(); i++)
      charFreq[s[i]]++;
   int result = 0;
   int flag = 0;
   for (auto i = charFreq.begin(); i != charFreq.end(); i++) {
      if (prime[i->second]) {
         result = result ^ i->second;
         flag = 1;
      }
   }
   if (!flag)
      return -1;
   return result;
}
int main(){
   string s = "tutorialspoint";
   cout<<"The XOR of frequencies of character which have prime frequencies is : ";
   cout<<findPrimeXOR(s);
   return 0;
}

Output

The XOR of frequencies of character which have prime frequencies is : 3