출처는 LeetCode입니다.

• https://leetcode.com/problems/two-sum/description/

🐧 Two Sum

문제 설명

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.

제한 사항

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

출력 예시

• 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]

나의 풀이

문제를 해결한 방법입니다.

https://leetcode.com/problems/two-sum/solutions/3992426/c-kor-twosum/

public class Solution {
    public int[] TwoSum(int[] nums, int target){
        Dictionary<int,int> numIndex = new Dictionary<int,int>();
        List<int> answer = new List<int>();

        for(int i = 0; i < nums.Length; i++){
            int ret = target - nums[i];
            if (numIndex.ContainsKey(ret)){
                answer.Add(numIndex[ret]);
                answer.Add(i);
                return answer.ToArray();
            }
            numIndex[nums[i]] = i;
        }
        return answer.ToArray();
    }
}