Set Matrix Zeroes

 1 public class Solution {
 2     /**
 3      * @param matrix:
 4      *            A list of lists of integers
 5      * @return: Void
 6      */
 7     public void setZeroes(int[][] matrix) {
 8         if (matrix == null || matrix.length == 0 || matrix[0].length == 0) return;
 9 
10         boolean firstRowZero = false;
11         boolean firstColumnZero = false;
12 
13         // set first row and column zero or not
14         for (int i = 0; i < matrix.length; i++) {
15             if (matrix[i][0] == 0) {
16                 firstColumnZero = true;
17                 break;
18             }
19         }
20 
21         for (int i = 0; i < matrix[0].length; i++) {
22             if (matrix[0][i] == 0) {
23                 firstRowZero = true;
24                 break;
25             }
26         }
27 
28         // mark zeros on first row and column
29         for (int i = 1; i < matrix.length; i++) {
30             for (int j = 1; j < matrix[0].length; j++) {
31                 if (matrix[i][j] == 0) {
32                     matrix[i][0] = 0;
33                     matrix[0][j] = 0;
34                 }
35             }
36         }
37 
38         // use mark to set elements
39         for (int i = 1; i < matrix.length; i++) {
40             for (int j = 1; j < matrix[0].length; j++) {
41                 if (matrix[i][0] == 0 || matrix[0][j] == 0) {
42                     matrix[i][j] = 0;
43                 }
44             }
45         }
46 
47         // set first column and row
48         if (firstColumnZero) {
49             for (int i = 0; i < matrix.length; i++)
50                 matrix[i][0] = 0;
51         }
52 
53         if (firstRowZero) {
54             for (int i = 0; i < matrix[0].length; i++)
55                 matrix[0][i] = 0;
56         }
57     }
58 }