136. Single Number

Problem Statement

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?

Thinking

哇，这个问题一开始怎么也没想到用异或（XOR）来做，在一个数组中其他的数字都是成对出现，要找出唯一一个是单个出现的。

异或：0^0 = 0，1^1 = 0，0 ^1 = 1 也就是说相同的异或结果是0，唯一一个没有相同的会返回他本身。

Solution

class Solution {    public int singleNumber(int[] nums) {        int fin = 0;        for(int i = 0;i < nums.length;i++){            fin ^= nums[i];        }        return fin;    }}