【codewar-4kyu】Snail 待學習

##題目描述

Description:

Snail Sort

Given an n x n array, return the array elements arranged from outermost elements to the middle element, traveling clockwise.

array = [[1,2,3],
         [4,5,6],
         [7,8,9]]
snail(array) #=> [1,2,3,6,9,8,7,4,5]

For better understanding, please follow the numbers of the next array consecutively:

array = [[1,2,3],
         [8,9,4],
         [7,6,5]]
snail(array) #=> [1,2,3,4,5,6,7,8,9]

 

This image will illustrate things more clearly:

 

NOTE: The idea is not sort the elements from the lowest value to the highest; the idea is to traverse the 2-d array in a clockwise snailshell pattern.

NOTE 2: The 0x0 (empty matrix) is represented as [[]]我好像最後仍是沒考慮空矩陣的處理。。。啊啊啊啊，路漫漫啊

##思路分析

忽然給我來了道4kyu....寫了半天寫了一長串，結果答案裏別人一句就寫完了。。。一句。。個人心裏是崩潰的

##代碼解析

Python，先貼別人的以便學習,第一個方案真是巧妙啊，服。每次遞歸取第一行，經過zip(*array[1:]）將剩下的行列轉換,經過[::-1]倒序輸出爲snail的argument，就又能夠取第一行了！

方案3思想和方案1一致，可是表達得直觀，更適合我等菜鳥學習。

1 #方案1
2 def snail(array):
3     return list(array[0]) + snail(zip(*array[1:])[::-1]) if array else []

 1 #方案2
 2 def snail(array):
 3     ret = []
 4     if array and array[0]:
 5         size = len(array)
 6         for n in xrange((size + 1) // 2):
 7             for x in xrange(n, size - n):
 8                 ret.append(array[n][x])
 9             for y in xrange(1 + n, size - n):
10                 ret.append(array[y][-1 - n])
11             for x in xrange(2 + n, size - n + 1):
12                 ret.append(array[-1 - n][-x])
13             for y in xrange(2 + n, size - n):
14                 ret.append(array[-y][n])
15     return ret

#方案3
def snail(array):
    a = []
    while array:
        a.extend(list(array.pop(0)))
        array = zip(*array)
        array.reverse()
    return a

方案3注意 extend，非 append。extend 的參數是 list.

下面是我本身的。。。徹底沒用到 python 高效的東西，只用了最最基本的函數，太弱智了

 1 #爲方便本地調試，加了不少 print，提交的時候須要註釋掉
 2 def snail(array):
 3     ans = []
 4     if len(array) == 1: # preven "index out of range"!!!
 5         ans = array[0]
 6         #print ans
 7         return ans
 8     len_row = len(array) - 1
 9     len_col = len(array[1]) - 1
10     all = (len_row + 1) * (len_col +1 )
11     #print len_col
12     over_row = 0
13     over_col = 0
14     while over_col <= len_col/2:
15         row = over_row  # current row
16         col = over_col
17         while over_col <= col < len_col - over_col:
18             now = array[row][col]
19             ans.append(now)
20             col += 1
21             #print 'now == ', now
22         #print 'this row over, col ==', col
23 
24         while over_row <= row < len_row - over_row :
25             now = array[row][col]
26             ans.append(now)
27             row += 1
28             #print 'now == ', now
29         #print 'this col over, row ==', row
30 
31         while over_col < col <= len_col - over_col:
32             now = array[row][col]
33             ans.append(now)
34             col -= 1
35             #print 'now == ', now
36         #print 'this reverse row over, col ==', col
37 
38         while over_row < row <= len_row - over_row:
39             now = array[row][col]
40             ans.append(now)
41             row -= 1
42             #print 'now == ', now
43     #print 'this reverse col over, col ==', row
44 
45         over_row += 1
46         over_col += 1
47         #print 'print over_row == ', over_row, 'print over_col == ', over_col
48     if len(ans) < all:
49         last = int(len_row/2)
50         ans.append(array[last][last])
51     #print ans
52     return ans