1380. Lucky Numbers in a Matrix ----------E

Q:

Given a m * n matrix of distinct numbers, return all lucky numbers in the matrix in any order.

A lucky number is an element of the matrix such that it is the minimum element in its row and maximum in its column.

 

Example 1:

Input: matrix = [[3,7,8],[9,11,13],[15,16,17]]
Output: [15]
Explanation: 15 is the only lucky number since it is the minimum in its row and the maximum in its column

Example 2:

Input: matrix = [[1,10,4,2],[9,3,8,7],[15,16,17,12]]
Output: [12]
Explanation: 12 is the only lucky number since it is the minimum in its row and the maximum in its column.

Example 3:

Input: matrix = [[7,8],[1,2]]
Output: [7]

 

Constraints:

• m == mat.length
• n == mat[i].length
• 1 <= n, m <= 50
• 1 <= matrix[i][j] <= 10^5.
• All elements in the matrix are distinct.

A:

class Solution {
public:
    vector<int> luckyNumbers (vector<vector<int>>& matrix) {
        vector<int> minRow ;
        for(auto & row : matrix){
             minRow.push_back(*std::min_element(row.begin(), row.end()));
        }
        unordered_set<int> mySet;
        for(int j =0;j<matrix[0].size();++j){
            int maxV = matrix[0][j];
            for(int i =1;i<matrix.size();++i){
                maxV = max(maxV, matrix[i][j]);
            }
            // cout<<maxV<<endl;
            mySet.insert(maxV);
        }
        vector<int> res;
        for(auto v : minRow){
            if(mySet.find(v) != mySet.end()){
                res.push_back(v);
            }
        }
        return res;
    }
};