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XOR of Prime Frequencies of Characters in a String
  • Last Updated : 11 Jun, 2019

Given a string containing only lowercase english alphabets. The task is to find the bitwise XOR of all the prime frequencies of the characters in the string. If no prime frequency is present, then print -1.

Examples:

Input : str = "gggggeeekkkks"
Output : 6

Input : str = "aabbbbw"
Output : -1

Approach:

Below is the implementation of the above approach:

C++




// C++ program to find XOR of Prime
// Frequencies of Characters in a String
#include <bits/stdc++.h>
using namespace std;
  
// Function to create Sieve to check primes
void SieveOfEratosthenes(bool prime[], int p_size)
{
    // false here indicates
    // that it is not prime
    prime[0] = false;
    prime[1] = false;
  
    for (int p = 2; p * p <= p_size; p++) {
  
        // If prime[p] is not changed,
        // then it is a prime
        if (prime[p]) {
  
            // Update all multiples of p,
            // set them to non-prime
            for (int i = p * 2; i <= p_size; i += p)
                prime[i] = false;
        }
    }
}
  
// Function to find XOR of prime frequencies
int xorOfPrime(string s)
{
    bool prime[100005];
    memset(prime, true, sizeof(prime));
  
    SieveOfEratosthenes(prime, 10005);
  
    int i, j;
  
    // map is used to store character
    // frequencies
    map<char, int> m;
    for (i = 0; i < s.length(); i++)
        m[s[i]]++;
  
    int result = 0;
    int flag = 0;
  
    // Traverse the map
    for (auto it = m.begin(); it != m.end(); it++) {
        // Calculate XOR of all prime
        // frequencies
        if (prime[it->second]) {
            result ^= it->second;
            flag = 1;
        }
    }
  
    if (!flag)
        return -1;
  
    return result;
}
  
// Driver code
int main()
{
    string s = "gggggeeekkkks";
  
    cout << xorOfPrime(s);
  
    return 0;
}


Java




// Java program to find XOR of Prime
// Frequencies of Characters in a String
import java.util.*;
  
class GFG
{
  
// Function to create Sieve to check primes
static void SieveOfEratosthenes(boolean prime[], int p_size)
{
    // false here indicates
    // that it is not prime
    prime[0] = false;
    prime[1] = false;
  
    for (int p = 2; p * p <= p_size; p++)
    {
  
        // If prime[p] is not changed,
        // then it is a prime
        if (prime[p])
        {
  
            // Update all multiples of p,
            // set them to non-prime
            for (int i = p * 2; i <= p_size; i += p)
                prime[i] = false;
        }
    }
}
  
// Function to find XOR of prime frequencies
static int xorOfPrime(char[] s)
{
    boolean []prime = new boolean[100005];
    for(int i = 0; i < 100005; i++)
        prime[i] = true;
  
    SieveOfEratosthenes(prime, 10005);
  
    int i, j;
  
    // map is used to store character
    // frequencies
    Map<Character,Integer> m = new HashMap<>();
    for (i = 0; i < s.length; i++)
    {
        if(m.containsKey(s[i]))
        {
            m.put(s[i], m.get(s[i])+1);
        }
        else
        {
            m.put(s[i], 1);
        }
    }
  
    int result = 0;
    int flag = 0;
  
    // Traverse the map
    for (Map.Entry<Character,Integer> entry : m.entrySet())
    {
        // Calculate XOR of all prime
        // frequencies
        if (prime[entry.getValue()]) 
        {
            result ^= entry.getValue();
            flag = 1;
        }
    }
  
    if (flag != 1)
        return -1;
  
    return result;
}
  
// Driver code
public static void main(String[] args) 
{
    char[] s = "gggggeeekkkks".toCharArray();
  
    System.out.println(xorOfPrime(s));
}
}
  
// This code has been contributed by 29AjayKumar


Python3




# Python3 program to find XOR of Prime 
# Frequencies of Characters in a String 
from collections import defaultdict
  
# Function to create Sieve to check primes 
def SieveOfEratosthenes(prime, p_size): 
  
    # False here indicates 
    # that it is not prime 
    prime[0] = False
    prime[1] = False
    p = 2
  
    while p * p <= p_size: 
  
        # If prime[p] is not changed, 
        # then it is a prime 
        if prime[p]: 
  
            # Update all multiples of p, 
            # set them to non-prime 
            for i in range(p * 2, p_size + 1, p): 
                prime[i] = False
                  
        p += 1
  
# Function to find XOR of prime frequencies 
def xorOfPrime(s):
  
    prime = [True] * 100005
      
    SieveOfEratosthenes(prime, 10005
  
    # map is used to store character frequencies 
    m = defaultdict(lambda:0
    for i in range(0, len(s)): 
        m[s[i]] += 1
  
    result = flag = 0
  
    # Traverse the map 
    for it in m: 
          
        # Calculate XOR of all prime frequencies 
        if prime[m[it]]: 
            result ^= m[it] 
            flag = 1
          
    if not flag: 
        return -1
  
    return result 
  
# Driver code 
if __name__ == "__main__"
  
    s = "gggggeeekkkks"
  
    print(xorOfPrime(s)) 
  
# This code is contributed by Rituraj Jain


C#




// C# program to find XOR of Prime
// Frequencies of Characters in a String
using System;     
using System.Collections.Generic;
  
class GFG
{
  
// Function to create Sieve to check primes
static void SieveOfEratosthenes(Boolean []prime, int p_size)
{
    // false here indicates
    // that it is not prime
    prime[0] = false;
    prime[1] = false;
  
    for (int p = 2; p * p <= p_size; p++)
    {
  
        // If prime[p] is not changed,
        // then it is a prime
        if (prime[p])
        {
  
            // Update all multiples of p,
            // set them to non-prime
            for (int i = p * 2; i <= p_size; i += p)
                prime[i] = false;
        }
    }
}
  
// Function to find XOR of prime frequencies
static int xorOfPrime(char[] s)
{
    Boolean []prime = new Boolean[100005];
    for(int i = 0; i < 100005; i++)
        prime[i] = true;
  
    SieveOfEratosthenes(prime, 10005);
  
      
  
    // map is used to store character
    // frequencies
    Dictionary<char, int> mp = new Dictionary<char,int>();
    for (int i = 0; i < s.Length; i++)
        {
            if (mp.ContainsKey(s[i]))
            {
                var v = mp[s[i]] + 1;
                mp.Remove(s[i]);
                mp.Add(s[i], v);
            
            else
            {
                mp.Add(s[i], 1);
            }
        }
  
    int result = 0;
    int flag = 0;
  
    // Traverse the map
    foreach(KeyValuePair<char, int> entry in mp)
    {
        // Calculate XOR of all prime
        // frequencies
        if (prime[entry.Value]) 
        {
            result ^= entry.Value;
            flag = 1;
        }
    }
  
    if (flag != 1)
        return -1;
  
    return result;
}
  
// Driver code
public static void Main(String[] args) 
{
    char[] s = "gggggeeekkkks".ToCharArray();
  
    Console.WriteLine(xorOfPrime(s));
}
}
  
// This code contributed by Rajput-Ji


Output:

6

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