136. Single Number

题目分析

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?
思路参考

代码

public class Solution {
    public int singleNumber(int[] A) {
        int res = 0;
        for(int a : A) {
            res ^= a;
        }
        return res;
    }
}