268. Missing Number

Problem Description
https://leetcode.com/problems/missing-number/description/

class Solution {
public:
    int missingNumber(vector<int>& nums) {
        int answer = nums.size();
        
        for (int i = 0; i < nums.size(); ++i) {
            answer ^= i;
            answer ^= nums[i];
        }

        return answer;
    }
};