class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        map<int, vector<int>> mp;
        int n = nums.size();
        for (int i = 0; i < n; i ++) {
            mp[nums[i]].push_back(i);
        }
        for (int i = 0; i < n; i ++) {
            int d = target - nums[i];
            if(nums[i] != d && mp[d].size()) return {i, mp[d][0]};
            if(nums[i] == d && mp[d].size() >= 2) {
                if(i == mp[d][0]) return {i, mp[d][1]};
                else return {i, mp[d][0]};
            }
        }
        return {};
    }
};