[leectode 2022.2.15] lucky numbers in the matrix

To give you one m * n Matrix , The number in the matrix Each are not identical . Please press arbitrarily Return all the lucky numbers in the matrix in order .

Lucky number refers to the elements in the matrix that meet the following two conditions at the same time ：

The smallest of all elements in the same row
The largest of all elements in the same column

Example 1：

Input ：matrix = [[3,7,8],[9,11,13],[15,16,17]]
Output ：[15]
explain ：15 Is the only lucky number , Because it is the smallest value in its row , It is also the maximum value in the column .
Example 2：

Input ：matrix = [[1,10,4,2],[9,3,8,7],[15,16,17,12]]
Output ：[12]
explain ：12 Is the only lucky number , Because it is the smallest value in its row , It is also the maximum value in the column .
Example 3：

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

Tips ：

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

java Code ：

class Solution {
    // Pretreated every 行 Array of minimum values  \textit{minRow}minRow  And an array of maximum values per column  \textit{maxCol}maxCol,
    // among  \textit{minRow}[i]minRow[i]  It means the first one  ii 行 The minimum value of ,\
    //textit{maxCol}[j]maxCol[j]  It means the first one  jj  The maximum value of the column .
    // ergodic matrix  \textit{matrix}matrix, If  \textit{matrix}[i][j]matrix[i][j]  At the same time satisfy  \textit{matrix}[i][j]=\textit{minRow}[i]matrix[i][j]=minRow[i]  and  \textit{matrix}[i][j] = \textit{maxCol}[j]matrix[i][j]=maxCol[j], that  \textit{matrix}[i][j]matrix[i][j]  Is the lucky number in the matrix , Add the returned results .
    public List<Integer> luckyNumbers (int[][] matrix) {
        int m = matrix.length, n = matrix[0].length;
        int[] minRow = new int[m];
        Arrays.fill(minRow, Integer.MAX_VALUE);
        int[] maxCol = new int[n];
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                minRow[i] = Math.min(minRow[i], matrix[i][j]);
                maxCol[j] = Math.max(maxCol[j], matrix[i][j]);
            }
        }
        List<Integer> ret = new ArrayList<Integer>();
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (matrix[i][j] == minRow[i] && matrix[i][j] == maxCol[j]) {
                    ret.add(matrix[i][j]);
                }
            }
        }
        return ret;
    }
}