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 resultsreturn result;}
Another Solution:
function twoSum(nums, target){// a map that holds the numbers and their indiceslet 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); }
