Leetcode 73. Set Matrix Zeroes

 1 class Solution:
 2     def setZeroes(self, matrix: List[List[int]]) -> None:
 3         """
 4         Do not return anything, modify matrix in-place instead.
 5         """
 6         first_row, first_col = False, False
 7         
 8         # check the first row and column first
 9         for i in range( len( matrix ) ):
10             if matrix[i][0] == 0:
11                 first_col = True;
12                 break;
13                 
14         for i in range( len( matrix[0] ) ):
15             if matrix[0][i] == 0:
16                 first_row = True;
17                 break;
18                 
19         # use the first row and column as marker
20         for i in range( 1, len( matrix ) ):
21             for j in range( 1, len( matrix[0] ) ):
22                 if matrix[i][j] == 0:
23                     matrix[i][0], matrix[0][j] = 0, 0;
24         
25         for i in range( 1, len( matrix ) ):
26             for j in range( 1, len( matrix[0] ) ):
27                 if matrix[i][0] == 0 or matrix[0][j] == 0:
28                     matrix[i][j] = 0
29                     
30         if first_row:
31             for i in range( len( matrix[0] ) ):
32                 matrix[0][i] = 0;
33                 
34         if first_col:
35             for i in range( len( matrix ) ):
36                 matrix[i][0] = 0;