1863. Sum of All Subset XOR Totals

The XOR total of an array is defined as the bitwise XOR of all its elements, or 0 if the array is empty.

• For example, the XOR total of the array [2,5,6] is 2 XOR 5 XOR 6 = 1.

Given an array nums, return the sum of all XOR totals for every subset of nums.

Note: Subsets with the same elements should be counted multiple times.

An array a is a subset of an array b if a can be obtained from b by deleting some (possibly zero) elements of b.

class Solution {
    int res = 0;
    void dfs(int left, int start, int XOR, vector<int>& nums) {
        if(!left) {
            res += XOR;
            return;
        }
        for(int i = start; i <= nums.size() - left; i++) {
            dfs(left - 1, i + 1, XOR xor nums[i], nums);
        }
    }
public:
    int subsetXORSum(vector<int>& nums) {
        for(int i = 1; i <= nums.size(); i++) {
            dfs(i, 0, 0, nums);
        }

        return res;
    }
};