single-number

题目描述

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?

代码

public int singleNumber(int[] a) {
        if(a==null)return 0;
        int result=0;
        for (int i = 0; i < a.length; i++) {
            result^=a[i];
        }
        return result;
    }