Python3解《剑指》问题：“遇到奇数移至最前，遇到偶数移至最后”

[本文出自天外归云的博客园]

看到一个《剑指Offer》上的问题：“遇到奇数移至最前，遇到偶数移至最后。”

我做了两种解法。一种是利用python内置函数，移动过程用了插入法，很简单。另一种是自定义与数字相关的类与函数，移动的过程用了指针思想。

代码如下：

'''
解法1：利用python中与列表相关的内置函数
'''
from collections import deque


def move_numbers(numbers: list, new_numbers=deque()):
    numbers = deque(numbers)
    while len(numbers) > 0:
        if numbers[0] % 2 == 0:
            number = numbers.popleft()
            new_numbers.append(number)
        else:
            number = numbers.popleft()
            new_numbers.appendleft(number)
    print(list(new_numbers))


'''
解法2：自定义与数字相关的类与函数
'''


class Numbers:
    header = None
    tail = None
    numbers = None

    class Number:
        def __init__(self, value):
            self.value = value
            self.next = None

    def __init__(self, *args):
        self.numbers = tuple([Numbers.Number(arg) for arg in args])
        self.install(self.numbers)

    def install(self, args: tuple):
        for i in range(len(args)):
            number = args[i]
            if i == 0 and len(args) > 1:
                number.next = args[i + 1]
                self.header = number
            if i > 0 and i < len(args) - 1:
                number.next = args[i + 1]
            if i == len(args) - 1 and len(args) > 1:
                self.tail = number

    def show(self):
        subs = []
        index = self.header
        while index:
            subs.append(index.value)
            index = index.next
        print(subs)

    def move(self):
        index = self.header
        new_header = None
        for i in range(len(self.numbers)):
            _next = index.next
            if index.value % 2 == 0:
                index.next = None
                self.tail.next = index
                self.tail = index
            if index.value % 2 != 0 and i != 0:
                if new_header:
                    index.next = new_header
                    new_header = index
                else:
                    new_header = index
                    new_header.next = self.header
                self.header = new_header
            index = _next
        self.show()


'''
题目：
    遇到奇数移动到最前面
    遇到偶数移动到最后面
'''
if __name__ == '__main__':
    numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 0]

    # 解法1
    move_numbers(numbers)

    # 解法2
    Numbers(*numbers).move()

其中：

1. 内置数据类型collections.deque是python中的队列，在队头插入和弹出元素比list的insert和pop操作效率高

2. 在main函数中将list类型的numbers转化为*args进行Numbers类对象初始化