1.7 Matrix Zero

 1 public static void matrixZero(int[][] matrix) {
 2     if (matrix.length == 0 || matrix[0].length == 0)
 3         return;
 4 
 5     int m = matrix.length;
 6     int n = matrix[0].length;
 7     boolean rowZero = false;
 8     boolean colZero = false;
 9 
10     // save first row and first col
11     for (int i = 0; i < m; i++)
12         if (matrix[i][0] == 0)
13             rowZero = true;
14     for (int i = 0; i < n; i++)
15         if (matrix[0][i] == 0)
16             colZero = true;
17 
18     for (int i = 0; i < m; i++) {
19         for (int j = 0; j < n; j++) {
20             if (matrix[i][j] == 0) {
21                 matrix[i][0] = 0;
22                 matrix[0][j] = 0;
23             }
24         }
25     }
26 
27     for (int i = 1; i < m; i++) {
28         if (matrix[i][0] == 0)
29             for (int j = 1; j < n; j++) {
30                 matrix[i][j] = 0;
31             }
32     }
33 
34     for (int i = 1; i < n; i++) {
35         if (matrix[0][i] == 0)
36             for (int j = 1; j < m; j++) {
37                 matrix[j][i] = 0;
38             }
39     }
40 
41     if (rowZero) {
42         for (int i = 0; i < m; i++)
43             matrix[i][0] = 0;
44     }
45 
46     if (colZero) {
47         for (int i = 0; i < n; i++)
48             matrix[0][i] = 0;
49     }
50 }