Today I have done leetcode's July LeetCoding Challenge with cpp.

July LeetCoding Challenge 19

Description

Lucky Numbers in a Matrix

Given an m x 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]
Explanation: 7 is the only lucky number since it is the minimum in its row and the maximum in its column.

Constraints:

• m == mat.length
• n == mat[i].length
• 1 <= n, m <= 50
• 1 <= matrix[i][j] <= 105.
• All elements in the matrix are distinct.

Solution

class Solution {
public:
  vector<int> luckyNumbers (vector<vector<int>>& matrix) {
    int rows = matrix.size();
    int cols = matrix.front().size();
    vector<int> rowMin(rows), colMax(cols);
    for(int i = 0; i < rows; ++i) {
      int result = matrix[i][0];
      for(auto i : matrix[i]) {
        result = min(result, i);
      }
      rowMin[i] = result;
    }
    for(int i = 0; i < cols; ++i) {
      int result = matrix[0][i];
      for(int j = 0; j < rows; ++j) {
        result = max(result, matrix[j][i]);
      }
      colMax[i] = result;
    }
    vector<int> answer;
    for(auto i : rowMin) {
      for(auto j : colMax) {
        if(i == j) answer.push_back(i);
      }
    }
    return answer;
  }
};