leetcode73 Set Matrix Zeroes

 1 """
 2 Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in-place.
 3 Example 1:
 4 Input:
 5 [
 6   [1,1,1],
 7   [1,0,1],
 8   [1,1,1]
 9 ]
10 Output:
11 [
12   [1,0,1],
13   [0,0,0],
14   [1,0,1]
15 ]
16 Example 2:
17 Input:
18 [
19   [0,1,2,0],
20   [3,4,5,2],
21   [1,3,1,5]
22 ]
23 Output:
24 [
25   [0,0,0,0],
26   [0,4,5,0],
27   [0,3,1,0]
28 ]
29 """
30 """
31 自己的方法：一遍AC
32 空间复杂度为O(m*n),需要进一步优化
33 """
34 class Solution:
35     def setZeroes(self, matrix):
36         """
37         Do not return anything, modify matrix in-place instead.
38         """
39         queue = set()
40         for i in range(len(matrix)):
41             for j in range(len(matrix[0])):
42                 if matrix[i][j] == 0:
43                     queue.add((i, j))
44         for x, y in queue:
45             for n in range(len(matrix[x])):
46                 matrix[x][n] = 0
47             for m in range(len(matrix)):
48                 matrix[m][y] = 0
49 """
50 解法二：自己优化了一下
51 """
52 class Solution2:
53     def setZeroes(self, matrix):
54         """
55         Do not return anything, modify matrix in-place instead.
56         """
57         row = set()
58         col = set()
59         for i in range(len(matrix)):
60             for j in range(len(matrix[0])):
61                 if matrix[i][j] == 0:
62                     row.add(i)
63                     col.add(j)
64         for x in row:
65             matrix[x] = [0]*len(matrix[x])
66         for y in col:
67             for i in range(len(matrix)):
68                 matrix[i][y] = 0
69 """
70 解法三：空间复杂度最低
71 将需要改变的值先变为'a'
72 最后再遍历一遍将值为'a'的变为0
73 """
74 class Solution3:
75     def setZeroes(self, matrix):
76         """
77         Do not return anything, modify matrix in-place instead.
78         """
79         row = len(matrix)
80         col = len(matrix[0])
81         for i in range(row):
82             for j in range(col):
83                 if matrix[i][j] == 0:
84                     for temp in range(row):
85                         if matrix[temp][j] != 0:
86                             matrix[temp][j] = 'a'
87                     for temp in range(col):
88                         if matrix[i][temp] != 0:
89                             matrix[i][temp] = 'a'
90         for i in range(row):
91             for j in range(col):
92                 if matrix[i][j] == 'a':
93                     matrix[i][j] = 0