Problem of The Day: Two Sum

Problem Statement

leetcode problem link

Solution [Accepted]

public class Solution {
    public int[] TwoSum(int[] nums, int target) {
        Dictionary<int, int> seen = new Dictionary<int, int>();
        for (int i = 0; i < nums.Length; i++) {
            int complement = target - nums[i];
            if (seen.ContainsKey(complement)) {
                return [i , seen[complement]];
            }
            seen[nums[i]] = i;
        }
        return [];
    }
}

Editorial

Approach 3: One-pass Hash Table

public class Solution {
    public int[] TwoSum(int[] nums, int target) {
        Dictionary<int, int> map = new Dictionary<int, int>();
        for (int i = 0; i < nums.Length; i++) {
            int complement = target - nums[i];
            if (map.ContainsKey(complement)) {
                return new int[] { map[complement], i };
            }
            map[nums[i]] = i;
        }
        // Return an empty array if no solution is found
        return new int[] {};
    }
}

class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:
        hashmap = {}
        for i in range(len(nums)):
            complement = target - nums[i]
            if complement in hashmap:
                return [i, hashmap[complement]]
            hashmap[nums[i]] = i
        # Return an empty list if no solution is found
        return []