두 합계 - O(n) 솔루션

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {



        unordered_map<int, int> hash;
        vector<int> result;

        for (int i = 0; i < nums.size(); ++i)
        {
            int numToFind = target - nums[i];

            if (hash.find(numToFind) != hash.end())
            {
                result.push_back(hash[numToFind]);
                result.push_back(i);
                return result;
            }
            else
            {
                hash[nums[i]] = i;
            }
        }



        return result;

    }
};