LeetCode 1835. Find XOR Sum of All Pairs Bitwise AND

The XOR sum of a list is the bitwise XOR of all its elements. If the list only contains one element, then its XOR sum will be equal to this element.

• For example, the XOR sum of [1,2,3,4] is equal to 1 XOR 2 XOR 3 XOR 4 = 4, and the XOR sum of [3] is equal to 3.

You are given two 0-indexed arrays arr1 and arr2 that consist only of non-negative integers.

Consider the list containing the result of arr1[i] AND arr2[j] (bitwise AND) for every (i, j) pair where 0 <= i < arr1.length and 0 <= j < arr2.length.

Return the XOR sum of the aforementioned list.

Example 1:

Input: arr1 = [1,2,3], arr2 = [6,5]
Output: 0
Explanation: The list = [1 AND 6, 1 AND 5, 2 AND 6, 2 AND 5, 3 AND 6, 3 AND 5] = [0,1,2,0,2,1].
The XOR sum = 0 XOR 1 XOR 2 XOR 0 XOR 2 XOR 1 = 0.

Example 2:

Input: arr1 = [12], arr2 = [4]
Output: 4
Explanation: The list = [12 AND 4] = [4]. The XOR sum = 4.

Constraints:

• 1 <= arr1.length, arr2.length <= 105

• 0 <= arr1[i], arr2[j] <= 109

Solution

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class Solution {
public:
    int getXORSum(vector<int>& arr1, vector<int>& arr2) {
        vector<int> bits(32, 0);
        for (int v : arr2) {
            int pos = 0;
            while (v > 0) {
                if (v & 1) {
                    bits[pos]++;
                }
                v = v >> 1;
                pos++;
            }
        }
        
        int res = 0;
        
        for (int v : arr1) {
            int pos = 0;
            int tmp = 0;
            while (v > 0) {
                if (v & 1) {
                    if (bits[pos] % 2 == 1) {
                        tmp |= (1 << pos);
                    }
                }
                v = v >> 1;
                pos++;
            }
            
            res ^= tmp;
        }
        
        return res;
    }
};