Description
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
C++
class Solution {
public:
vector<int> luckyNumbers (vector<vector<int>>& matrix) {
int rows = matrix.size(), cols = matrix[0].size();
vector<int> rowMin(rows, INT_MAX), colMax(cols, INT_MIN);
vector<int> res;
for (int i = 0; i < rows; i++) {
for (int j = 0; j < cols; j++) {
rowMin[i] = min(rowMin[i], matrix[i][j]);
colMax[j] = max(colMax[j], matrix[i][j]);
}
}
for (int i = 0; i < rows; i++)
for (int j = 0; j < cols; j++)
if (matrix[i][j] == rowMin[i] && matrix[i][j] == colMax[j]) {
res.push_back(matrix[i][j]);
break;
}
return res;
}
};
Python3
class Solution:
def luckyNumbers (self, matrix: List[List[int]]) -> List[int]:
r,c = len(matrix), len(matrix[0])
col = [0] * c
# calculate max col
for i in range(c):
col[i] = max([matrix[j][i] for j in range(r)])
res = []
for i in range(r):
for j in range(c):
if min(matrix[i]) == matrix[i][j] and col[j] == matrix[i][j]:
res.append(matrix[i][j])
return res