# Pairs with given XOR

Given an array A[] of size N of distinct positive integers and a number X, find the number of pairs of integers in the array whose XOR is equal to X.

Example 1:

```
Input:
N = 6
A[] = {5, 4, 10, 15, 7, 6}
X = 5
Output: 1
Explanation: (10 ^ 15) = 5
```

Example 2:

```
Input:
N = 6
A[] = {3, 6, 8, 10, 15, 50}
X = 5
Output: 2
Explanation: (3 ^ 6) = 5 and (10 ^ 15) = 5
```

**c++ implementation:**

**int countPair(int n, int a[], int x)
{
unordered_map<int,int>m;
int c=0;
for(int i=0;i<n;i++)
{
if(m.find(x^a[i])!=m.end())
c=c+m[x^a[i]];
m[a[i]]++;
}
return c;
}**

**Time Complexity:**O(n)

**space Complexity: **O(n)