73. Set Matrix Zeroes

To solve it in place, I'll use the first row and first column to record the 0s.

1:  class Solution {  
2:  public:  
3:    void setZeroes(vector<vector<int>>& matrix) {  
4:      int rows = matrix.size();  
5:      int cols = matrix[0].size();  
6:      bool col0 = true, row0 = true;  
7:      for (int i = 0; i < rows; i++) {  
8:        if (matrix[i][0] == 0) {  
9:          col0 = false;  
10:          break;  
11:        }  
12:      }  
13:      for (int j = 0; j < cols; j++) {  
14:        if (matrix[0][j] == 0) {  
15:          row0 = false;  
16:          break;  
17:        }  
18:      }  
19:      for (int i = 0; i < rows; i++) {  
20:        for (int j = 0; j < cols; j++) {  
21:          if (matrix[i][j] == 0) {  
22:            matrix[i][0] = 0;  
23:            matrix[0][j] = 0;  
24:          }  
25:        }  
26:      }  
27:      for (int i = 1; i < rows; i++) {  
28:        if (matrix[i][0] == 0) {  
29:          for (int j = 1; j < cols; j++) {  
30:            matrix[i][j] = 0;  
31:          }  
32:        }  
33:      }  
34:      for (int j = 1; j < cols; j++) {  
35:        if (matrix[0][j] == 0) {  
36:          for (int i = 1; i < rows; i++) {  
37:            matrix[i][j] = 0;  
38:          }  
39:        }  
40:      }  
41:      if (!col0) {  
42:        for (int i = 0; i < rows; i++) {  
43:          matrix[i][0] = 0;  
44:        }  
45:      }  
46:      if (!row0) {  
47:        for (int j = 0; j < cols; j++) {  
48:          matrix[0][j] = 0;  
49:        }  
50:      }  
51:    }  
52:  };