0001_twoSum.js

/**
 * @param {number[]} nums Array of integers.
 * @param {number} target Two numbers from nums array should add up to this target.
 * @return {number[]} Indices of two numbers from 'nums' that add up to 'target'
 * @summary Two Sum {@link https://leetcode.com/problems/two-sum/}
 * @description Given an array of integers, return indices of the two numbers such that they add up to a specific target.
 * Space O(n) - hash object storing data will have no more than n elements.
 * Time O(n) - one iteration of n elements.
 */
const twoSum = (nums, target) => {
  const hash = {};
  let index, remaining;

  for (index = 0; index < nums.length; index++) {
    remaining = target - nums[index];

    if (hash[remaining] !== undefined) {
      return [hash[remaining], index];
    }

    hash[nums[index]] = index;
  }
};