Two Sum

Given an array A and an integer target, find the indices of the two numbers in the array whose sum is equal to the given target.

Note: The problem has exactly one solution. Do not use the same element twice.

pair<int,int> twoSum(vector<int> &A, int target) {
    unordered_map<int, int> mp;
	for(int i = 0; i < A.size(); i++) {
		if(mp.count(target - A[i])) return {mp[target - A[i]], i};
		mp[A[i]] = i;
	}
	return {-1,-1};
}