Find the XOR of first N Prime Numbers | C ++ implementation of the approach ; Create a boolean array " prime [ 0 . . n ] " and initialize all entries it as true . A value in prime [ i ] will finally be false if i is Not a prime , else true . ; If prime [ p ] is not changed , then it is a prime ; Set all multiples of p to non - prime ; Function to return the xor of 1 st N prime numbers ; Count of prime numbers ; XOR of prime numbers ; If the number is prime xor it ; Increment the count ; Get to the next number ; Driver code ; Create the sieve ; Find the xor of 1 st n prime numbers
#include <bits/stdc++.h> NEW_LINE using namespace std ; #define MAX  10000 NEW_LINE bool prime [ MAX + 1 ] ; void SieveOfEratosthenes ( ) { memset ( prime , true , sizeof ( prime ) ) ; prime [ 1 ] = false ; for ( int p = 2 ; p * p <= MAX ; p ++ ) { if ( prime [ p ] == true ) { for ( int i = p * 2 ; i <= MAX ; i += p ) prime [ i ] = false ; } } } int xorFirstNPrime ( int n ) { int count = 0 , num = 1 ; int xorVal = 0 ; while ( count < n ) { if ( prime [ num ] ) { xorVal ^= num ; count ++ ; } num ++ ; } return xorVal ; } int main ( ) { SieveOfEratosthenes ( ) ; int n = 4 ; cout << xorFirstNPrime ( n ) ; return 0 ; }