136. Single Number

1. 问题

   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?

2. 描述

   这个问题主要考察对于算术运算符的应用，注意任何数与0进行异或为其本身，两个相同的数进行异或为0，因此将数组中的所有的数进行异或剩余的为出现一次的

3. 代码

   public static int singleNumber(int[] nums) {        int a = 0;        for (int num : nums) {            a = a ^ num;        }        return a;    }