using System.Collections.Generic;

// Problem Description:-

// https://leetcode.com/problems/two-sum/submissions/1169601932/

public class Solution {

    public int[] TwoSum(int[] nums, int target) {

        Dictionary<int, int> numToIndex = new Dictionary<int, int>();

        for (int i = 0; i < nums.Length; i++) {

            int complement = target - nums[i];

            if (numToIndex.ContainsKey(complement)) {

                return new int[] { numToIndex[complement], i };

            }

            numToIndex[nums[i]] = i;

        }

        return null;

    }

}