singleNumber.js

/*
Given a non-empty 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?

Example 1:

Input: [2,2,1]
Output: 1
Example 2:

Input: [4,1,2,1,2]
Output: 4
*/

//Answer//
/**
 * @param {number[]} nums
 * @return {number}
 */
var singleNumber = function(nums) {
return nums.filter(x=>nums.indexOf(x)===nums.lastIndexOf(x))[0]
};

//Or//

var singleNumber = function(nums) {
    for (let i = 0; i < nums.length ; i++) {
if(nums.indexOf(nums[i])===nums.lastIndexOf(nums[i])){return nums[i]}
} 
};