two sum problem always returns empty array

August 15, 2023

It always returns empty array.

Implement solution to two sum problem in javascript

function twoSum(nums, target) {
  const map = {};

  for (let i = 0; i < nums.length; i++) {
    let comp = target - nums[i];
    if (map[comp] !== undefined) {
      return [map[comp], i];
    } else {
      map[comp] = i;
    }
  }
  return [];
}

console.log(twoSum([2, 7, 11, 15], 9));

>Solution :

Your function logic is correct but there seems to be a small mistake. Instead of storing the complement of the number (comp) in the map, you should store the actual number in the map.

Here’s the corrected solution:

function twoSum(nums, target) {
  const map = {};

  for (let i = 0; i < nums.length; i++) {
    let comp = target - nums[i];
    if (map[comp] !== undefined) {
      return [map[comp], i];
    } else {
      map[nums[i]] = i;  // Store the actual number, not its complement.
    }
  }
  return [];
}

console.log(twoSum([2, 7, 11, 15], 9));  // Should return [0, 1]