[LeetCode]Missing Number

Given an array containing n distinct numbers taken from 0, 1, 2, ..., n, find the one that is missing from the array.

For example,
Given nums = [0, 1, 3] return 2.

Note:

Your algorithm should run in linear runtime complexity. Could you implement it using only constant extra space complexity?

首先对0～ n内数字做异或，在对数组内数字做异或。等价与在Single Number 1，在一堆重复数字中找1个。

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