leetcode54 Spiral Matrix

 1 """
 2 Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.
 3 Example 1:
 4 Input:
 5 [
 6  [ 1, 2, 3 ],
 7  [ 4, 5, 6 ],
 8  [ 7, 8, 9 ]
 9 ]
10 Output: [1,2,3,6,9,8,7,4,5]
11 Example 2:
12 Input:
13 [
14   [1, 2, 3, 4],
15   [5, 6, 7, 8],
16   [9,10,11,12]
17 ]
18 Output: [1,2,3,4,8,12,11,10,9,5,6,7]
19 """
20 class Solution:
21     def spiralOrder(self, matrix):
22         if not matrix:
23             return []
24         res = []
25         row_end = len(matrix)-1
26         col_end = len(matrix[0])-1
27         row_begin, col_begin = 0, 0
28         while row_begin <= row_end and col_begin <= col_end:#!!!关键
29             # 向右
30             j = col_begin
31             while j <= col_end:
32                 res.append(matrix[row_begin][j])
33                 j += 1
34             row_begin += 1
35             # 向下
36             i = row_begin
37             while i <= row_end:
38                 res.append(matrix[i][col_end])
39                 i += 1
40             col_end -= 1
41             if row_begin <= row_end:
42             # 向左
43                 j = col_end
44                 while j >= col_begin:
45                     res.append(matrix[row_end][j])
46                     j -= 1
47             row_end -= 1
48             if col_begin <= col_end:
49             # 向上
50                 i = row_end
51                 while i >= row_begin:
52                     res.append(matrix[i][col_begin])
53                     i -= 1
54             col_begin += 1
55         return res