#include <unordered_map>

using namespace std;

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        unordered_map<int, int> diffs = {};
        for (int i = 0; i < nums.size(); i++) {
            int actual_number = nums[i];
            unordered_map<int, int>::iterator iter = diffs.find(actual_number);
            if (iter == diffs.end()) {
                diffs.insert(make_pair(target - actual_number, i));
            } else {
                return vector<int>{iter->second, i};
            }
        }
        return vector<int>{0, 0};
    }
};