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

Description

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.

Example 1:

Input: arr = [2,3,1,6,7]
Output: 4
Explanation: The triplets are (0,1,2), (0,2,2), (2,3,4) and (2,4,4)

Example 2:

Input: arr = [1,1,1,1,1]
Output: 10

Constraints:

1 <= arr.length <= 300
1 <= arr[i] <= 10⁸

Solution

count-triplets-that-can-form-two-arrays-of-equal-xor.py

class Solution:
    def countTriplets(self, arr: List[int]) -> int:
        res = 0
        for i in range(len(arr)):
            x = arr[i]
            for j in range(i+1, len(arr)):
                x ^= arr[j]
                if x == 0:
                    res += (j - i)

        return res