2588. Count the Number of Beautiful Subarrays

You are given a 0-indexed integer array nums. In one operation, you can:

• Choose two different indices i and j such that 0 <= i, j < nums.length.
• Choose a non-negative integer k such that the kth bit (0-indexed) in the binary representation of nums[i] and nums[j] is 1.
• Subtract 2k from nums[i] and nums[j].

A subarray is beautiful if it is possible to make all of its elements equal to 0 after applying the above operation any number of times.

Return the number of beautiful subarrays in the array nums.

A subarray is a contiguous non-empty sequence of elements within an array.

class Solution {
public:
    long long beautifulSubarrays(vector<int>& nums) {
        long long bit = 0, res = 0;
        unordered_map<long long, long long> freq{{0,1}};
        for(auto n : nums) {
            bit ^= n;
            if(freq.count(bit)) res += freq[bit];
            freq[bit] += 1;
        }
        return res;
    }
};