1436 Destination City

Problem Statement

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.
Input: nums = [2,7,11,15], target = 9
Output: [0,1]


The BF solution would be to compare each element with each other element and see if they match the target. This approach is very inefficient with a BigO(N²) due to two nested for loops.
The recommended solution is to use a hashmap and check if target - current number is in the hashmap, if so return if not add the entry at i.


var twoSum = function(nums, target) {
    let hash = {}
    for (let i=0; i < nums.length; i++){
        if ((target - nums[i]) in hash){
            return [i, hash[target - nums[i]]]
        hash[nums[i]] = i




Hash table