Pairs_with_Xor.java

/*Pairs With Given Xor
Problem Description

Given an 1D integer array A containing N distinct integers.

Find the number of unique pairs of integers in the array whose XOR is equal to B.

NOTE:

Pair (a, b) and (b, a) is considered to be same and should be counted once.


Problem Constraints
1 <= N <= 105

1 <= A[i], B <= 107



Input Format
First argument is an 1D integer array A.

Second argument is an integer B.



Output Format
Return a single integer denoting the number of unique pairs of integers in the array A whose XOR is equal to B.



Example Input
Input 1:

 A = [5, 4, 10, 15, 7, 6]
 B = 5
Input 2:

 A = [3, 6, 8, 10, 15, 50]
 B = 5


Example Output
Output 1:

 1
Output 2:

 2


Example Explanation
Explanation 1:

 (10 ^ 15) = 5
Explanation 2:

 (3 ^ 6) = 5 and (10 ^ 15) = 5 */





public class Solution {
    public int solve(int[] A, int B) {
        
        HashMap<Integer, Integer> m = new HashMap<Integer, Integer>();
        int res = 0;
          for (int i = 0; i <A.length; i++)
          {
            int t =B^A[i];
            if (m.containsKey(t))
            {
                res++;
            }
             if(!m.containsKey(A[i]))
             {
               m.put(A[i],i);
             }
          }
        return res;
    }
}