two-sum.js

// Given an array of integers, return indices of the two numbers such that they add up to a specific target.
//
// You may assume that each input would have exactly one solution.
//
//
// Example:
//
// Given nums = [2, 7, 11, 15], target = 9,
//
// Because nums[0] + nums[1] = 2 + 7 = 9,
// return [0, 1].
//
//
//
//
// UPDATE (2016/2/13):
// The return format had been changed to zero-based indices. Please read the above updated description carefully.


/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number[]}
 */
var twoSum = function(nums, target) {
    const hmap = {}
    for (var idx=0; idx<nums.length; idx++) {
        var val = nums[idx]
        var delta = target - val
        var deltaIdx = hmap[delta]
        if (deltaIdx !== undefined && deltaIdx !== idx) {
            return [deltaIdx, idx]
        }
        hmap[val] = idx
    }
    return []
};