Generating Subsets using Backtracking

1863. Sum of All Subset XOR Totals
This is a good problem to grasp basics of backtracking

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.

Example 1:

Input: nums = [1,3]
Output: 6
Explanation: The 4 subsets of [1,3] are:
- The empty subset has an XOR total of 0.
- [1] has an XOR total of 1.
- [3] has an XOR total of 3.
- [1,3] has an XOR total of 1 XOR 3 = 2.
0 + 1 + 3 + 2 = 6

Example 2:

Input: nums = [5,1,6]
Output: 28
Explanation: The 8 subsets of [5,1,6] are:
- The empty subset has an XOR total of 0.
- [5] has an XOR total of 5.
- [1] has an XOR total of 1.
- [6] has an XOR total of 6.
- [5,1] has an XOR total of 5 XOR 1 = 4.
- [5,6] has an XOR total of 5 XOR 6 = 3.
- [1,6] has an XOR total of 1 XOR 6 = 7.
- [5,1,6] has an XOR total of 5 XOR 1 XOR 6 = 2.
0 + 5 + 1 + 6 + 4 + 3 + 7 + 2 = 28

Example 3:

Input: nums = [3,4,5,6,7,8]
Output: 480
Explanation: The sum of all XOR totals for every subset is 480.

class Solution {
    vector<vector<int>> subset;
    void backtrack(vector<int> &nums,vector<int> &current,int index){
        subset.push_back(current);
        for(int i = index; i < nums.size(); i++ ){
            current.push_back(nums[i]);
            backtrack( nums,  current, i+1);
            current.pop_back();
        }
    }
public:
    
    int subsetXORSum(vector<int>& nums) {
        vector<int> current;
        backtrack(nums,current,0);
        
        int total_sum = 0;
        for (const auto& sub : subset) {
            int xor_sum = 0;
            for (int num : sub) {
                //std::cout<<num<<" ";
                xor_sum ^= num;
            }
            //std::cout<<std::endl;
            total_sum += xor_sum;
        }
        
        return total_sum;
    }
};