136. 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?

Similar: 

137. Single Number II

260. Single Number III

268. Missing Number

287. Find the Duplicate Number

public class Solution {
    public int singleNumber(int[] nums) {
        int ret = nums[0];
        for (int i = 1; i < nums.length; i++) {
            ret ^= nums[i];
        }
        return ret;
    }
}