1442. Count Triplets That Can Form Two Arrays of Equal XOR

Given an array of integers arr.

We want to select three indices i, j and k where (0 <= i < j <= k < arr.length).

Let’s define a and b as follows:

• a = arr[i] ^ arr[i + 1] ^ … ^ arr[j - 1]
• b = arr[j] ^ arr[j + 1] ^ … ^ arr[k]

Note that ^ denotes the bitwise-xor operation.

Return the number of triplets (i, j and k) Where a == b.

class Solution {
public:
    int countTriplets(vector<int>& A) {
        A.insert(A.begin(), 0);
        int res = 0, n = A.size();
        for(int i = 1; i < n; i++) {
            A[i] ^= A[i-1];
        }
        for(int i = 0; i < n; i++) {
            for(int j = i + 1; j < n; j++) {
                if(A[i] == A[j]) res += j - i - 1;
            }
        }
        return res;
    }
};