Leetcode: Two Sum (JS)

Example 1:

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

Understanding the problem:

Per the example above, if we start with 2, and we want to reach 9 — we need to add 7 from the array. The indices for 2 and 7 are 0 and 1.

How do we do this?

function twoSum(nums, target){
// a map that holds the numbers and their indices
  let numberIndex = new Map();
// we need an array for our indices results
  let result = [];
// loop through the nums array
  for (let i=0; i < nums.length; i++){
//current element we're on
     let currentNum = nums[i];
// save the difference between the number we're on and the target
     let neededNum = target - currentNum;
// check to see if the map has the number we need
     if (numberIndex.has(neededNum)){
        result[0] = numberIndex.get(neededNum);
        result[1] = i;
        return result;
  }
     //if they don't match, add the current number & index to the map
     numberIndex.set(currentNum, i)
}

// return our indices results
return result;
}

Another Solution:

function twoSum(nums, target){
// a map that holds the numbers and their indices
let map = new Map();
 
// loop through the nums array
  for (let i = 0; i < nums.length; i++){
//current element we're on
    let currentNum = nums[i];
// save the difference between the number we're on and the target
    let neededNum = target — currentNum;
// check to see if the map has the number we need
        if (map.has(neededNum)){
// return our indices results
        return [i, map.get(neededNum)];
 }
//if they don't match, add the current number & index to the map
     map.set(currentNum, i);
 }

✨✨✨And that’s it!

Tish⚡️🎧🌙