【codewar-4kyu】Snail 待学习

##题目描述

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 [[]]我好像最后还是没考虑空矩阵的处理。。。啊啊啊啊，路漫漫啊

##思路分析

突然给我来了道4kyu....写了半天写了一长串，结果答案里别人一句就写完了。。。一句。。我的内心是崩溃的

##代码解析

Python，先贴别人的以便学习,第一个方案真是巧妙啊，服。每次递归取第一行，通过zip(*array[1:]）将剩下的行列转换,通过[::-1]倒序输出为snail的argument，就又可以取第一行了！

方案3思想和方案1一致，但是表达得直观，更适合我等菜鸟学习。

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

#方案2
def snail(array):
    ret = []
    if array and array[0]:
        size = len(array)
        for n in xrange((size + 1) // 2):
            for x in xrange(n, size - n):
                ret.append(array[n][x])
            for y in xrange(1 + n, size - n):
                ret.append(array[y][-1 - n])
            for x in xrange(2 + n, size - n + 1):
                ret.append(array[-1 - n][-x])
            for y in xrange(2 + n, size - n):
                ret.append(array[-y][n])
    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 的参数是 list.

下面是我自己的。。。完全没用到 python 高效的东西，只用了最最基本的函数，太弱智了

#为方便本地调试，加了很多 print，提交的时候需要注释掉
def snail(array):
    ans = []
    if len(array) == 1: # preven "index out of range"!!!
        ans = array[0]
        #print ans
        return ans
    len_row = len(array) - 1
    len_col = len(array[1]) - 1
    all = (len_row + 1) * (len_col +1 )
    #print len_col
    over_row = 0
    over_col = 0
    while over_col <= len_col/2:
        row = over_row  # current row
        col = over_col
        while over_col <= col < len_col - over_col:
            now = array[row][col]
            ans.append(now)
            col += 1
            #print 'now == ', now
        #print 'this row over, col ==', col

        while over_row <= row < len_row - over_row :
            now = array[row][col]
            ans.append(now)
            row += 1
            #print 'now == ', now
        #print 'this col over, row ==', row

        while over_col < col <= len_col - over_col:
            now = array[row][col]
            ans.append(now)
            col -= 1
            #print 'now == ', now
        #print 'this reverse row over, col ==', col

        while over_row < row <= len_row - over_row:
            now = array[row][col]
            ans.append(now)
            row -= 1
            #print 'now == ', now
    #print 'this reverse col over, col ==', row

        over_row += 1
        over_col += 1
        #print 'print over_row == ', over_row, 'print over_col == ', over_col
    if len(ans) < all:
        last = int(len_row/2)
        ans.append(array[last][last])
    #print ans
    return ans