Single Number

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： 遍历， 异或。Java XOR is ^;

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