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?

分析：

使用^即可，最后剩余的结果就是我们需要的。

/**
 * @param {number[]} nums
 * @return {number}
 */
var singleNumber = function(nums) {
    let result = 0;
    for(let i = 0; i <nums.length; i++) {
        result^= nums[i];
    }
    return result;
};

LeetCode 136. Single Number