1.cpp

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        unordered_map<int, int> map;
        for (int i = 0; i < nums.size(); ++i) {
            if (auto it = map.find(target - nums[i]); it != map.end())
                return {it->second, i};
            map[nums[i]] = i;
        }
        return {};
    }
};