【雙端隊列】用python實現雙端隊列

分別用有序列表和鏈實現了雙端隊列，主要包括首端加入/刪除、末端加入/刪除等功能。

方法一：有序列表的實現

class Deque(object):
    def __init__(self):
        self.data = []

    def __repr__(self):
        return str(self.data)

    def addRear(self, value):
        self.data.append(value)

    def addFront(self, value):
        self.data.insert(0, value)

    def removeRear(self):
        if self.isEmpty():
            raise IndexError("remove from empty deque")
        else:
            self.data.pop()

    def removeFront(self):
        if self.isEmpty():
            raise IndexError("remove from empty deque")
        else:
            self.data.pop(0)

    def isEmpty(self):
        return len(self.data) == 0

    def __len__(self):
        return len(self.data)

方法二：單鏈表的實現

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

class Deque(object):
    def __init__(self):
        self.head = None

    def __repr__(self):
        data_list = []
        current = self.head

        while current:
            data_list.append(current.value)
            current = current.next

        return str(data_list)

    def addRear(self, value):
        new_node = Node(value)
        if self.isEmpty():
            self.head = new_node

        else:
            current = self.head
            while current.next:
                current = current.next
            current.next = new_node

    def addFront(self,value):
        new_node = Node(value)
        if self.isEmpty():
            self.head = new_node

        else:
            current = self.head
            new_node.next = current
            self.head = new_node

    def removeRear(self):
        if self.isEmpty():
            raise IndexError("remove from empty deque")
        else:
            current = self.head
            if current.next is None:
                self.head = None
                return current.value

            else:
                while current.next.next:
                    current = current.next
                value = current.next.value
                current.next = None
                return value


    def removeFront(self):
        if self.isEmpty():
            raise IndexError("remove from empty deque")

        value = self.head.value
        self.head = self.head.next
        return value


    def isEmpty(self):
        return self.head is None


    def __len__(self):
        length = 0
        current = self.head
        while current:
            length += 1
            current = current.next
        return length