singleNumber.js

//////////////////////////////////////////////Single Number/////////////////////////////////////////////////
// Given a non-empty array of integers nums, every element appears twice except for one. Find that single one.
// You must implement a solution with a linear runtime complexity and use only constant extra space.
// Example 1:
// Input: nums = [2,2,1]
// Output: 1
// Example 2:
//
// Input: nums = [4,1,2,1,2]
// Output: 4
// Example 3:
//
// Input: nums = [1]
// Output: 1
// Constraints:
//
// 1 <= nums.length <= 3 * 104
// -3 * 104 <= nums[i] <= 3 * 104
// Each element in the array appears twice except for one element which appears only once.
const singleNumber = function(nums) {
    return nums.filter((v, i, a) => a.indexOf(v) === a.lastIndexOf(v))[0];
};

// console.log(singleNumber([2, 2, 1]));
// console.log(singleNumber([4,1,2,1,2]));
// console.log(singleNumber([1]));