Leetcode 268. Missing Number

https://leetcode.com/problems/missing-number/description/
如果sorted，这题用binary search更快
这里的解法就是用了bit manipulation里最常考的一个：
XOR: A ^ A = 0

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

136. Single Number
     用了一样的trick
     https://leetcode.com/problems/single-number/description/