1.two-sum.js

// https://leetcode.com/problems/two-sum/
// Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.
// You may assume that each input would have exactly one solution, and you may not use the same element twice.
// You can return the answer in any order.

// Example 1:
// Input: nums = [2,7,11,15], target = 9
// Output: [0,1]
// Explanation: Because nums[0] + nums[1] == 9, we return [0, 1].
// Example 2:
// Input: nums = [3,2,4], target = 6
// Output: [1,2]
// Example 3:
// Input: nums = [3,3], target = 6
// Output: [0,1]

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number[]}
 */
var twoSum = function (nums, target) {
  let numberMap = new Map();
  for (let index = 0; index < nums.length; index++) {
    el = nums[index];

    if (numberMap.has(target - el)) return [index, numberMap.get(target - el)];
    else numberMap.set(el, index);
  }

  return [];
};

twoSum([3, 2, 4], 6);