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,

#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