LeetCode Two Sum Problem Solution

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.

Example 1:

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

Example 2:

Input: nums = [3,2,4], target = 6
Output: [1,2]

Example 3:

Input: nums = [3,3], target = 6
Output: [0,1]

Constraints:

• 2 <= nums.length <= 104
• -109 <= nums[i] <= 109
• -109 <= target <= 109
• Only one valid answer exists.

Solutions:

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number[]}
 */
var twoSum = function(nums, target) {
    const numMap = new Map();

    for (let i=0; i<nums.length; i++) {
        const complement = target - nums[i];
        if(numMap.has(complement)) {

            // if the complement exists in the map then return i
            return [numMap.get(complement), i];
        }

        // now store the current number and its index in the map so we have,
        numMap.set(nums[i], i);
    }

    // if no solution will be foun
    return [];
};

const nums = [2,7,11,15];
const target = 9;

// now its time to console log the output
console.log(twoSum(nums, target));