Leetcode#73 Set Matrix Zeroes

原题地址

 

用矩形的第一行和第一列充当mask

 

代码：

 1 void setZeroes(vector<vector<int> > &matrix) {

 2         if (matrix.empty() || matrix[0].empty()) return;

 3         

 4         bool firstRow = false;

 5         bool firstCol = false;

 6         int m = matrix.size();

 7         int n = matrix[0].size();

 8         

 9         for (int i = 0; i < m; i++)

10             if (matrix[i][0] == 0) {

11                 firstCol = true;

12                 break;

13             }

14             

15         for (int j = 0; j < n; j++)

16             if (matrix[0][j] == 0) {

17                 firstRow = true;

18                 break;

19             }

20             

21         for (int i = 0; i < m; i++) {

22             for (int j = 0; j < n; j++) {

23                 if (matrix[i][j] == 0) {

24                     matrix[i][0] = 0;

25                     matrix[0][j] = 0;

26                 }

27             }

28         }

29         

30         for (int i = 1; i < m; i++)

31             if (matrix[i][0] == 0)

32                 for (int j = 1; j < n; j++)

33                     matrix[i][j] = 0;

34         

35         for (int j = 1; j < n; j++)

36             if (matrix[0][j] == 0)

37                 for (int i = 1; i < m; i++)

38                     matrix[i][j] = 0;

39         

40         if (firstCol)

41             for (int i = 0; i < m; i++)

42                 matrix[i][0] = 0;

43         if (firstRow)

44             for (int j = 0; j < n; j++)

45                 matrix[0][j] = 0;

46 }