leetcode刷题系列C++-single number I

Given an array of integers, every element appears twice except for one. Find that single one.

Note:
Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

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

异或运算，0根任何数异或都是任何数本身，异或符合交换律   a ^ b = b ^ a 。