2 Sum

2 Sum - InterviewBitInterviewBit

Using Map

C++

vector<int> Solution::twoSum(const vector<int> &A, int B) {
    map<int, int> indexOf;
    vector<int> res;
    
    for(int i = 0; i < A.size(); i++)
        if(indexOf.count(B - A[i])) {
            res.push_back(indexOf[B - A[i]] + 1);
            res.push_back(i + 1);
            break;
        } else if (!indexOf.count(A[i]))
            indexOf[A[i]] = i;
            
    return res;
}

Accepted

Time Complexity: $O(n)$​

Space Complexity: $O(n)$