数据结构与算法-简单双向循环链表实现

本文链接：https://blog.youkuaiyun.com/qq_41174308/article/details/90759761

本文深入探讨了数据结构中的双向循环链表，详细解释了其工作原理，并提供了简单的实现代码，帮助读者理解如何在实际编程中运用这种数据结构。

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双向循环链表

# coding :utf-8
class LinkListNode(object):
    """双向循环链表节点"""

    def __init__(self, value):
        # 上指针
        self.prev = None
        # 值
        self.value = value
        # 下指针
        self.next = None


class DoubleLoopLinkList(object):
    """双向循环链表"""

    def __init__(self):
        '''初始化链表'''
        self.__head = None

    def is_empty(self):
        '''判断链表是否为空'''
        return self.__head is None

    def length(self):
        '''获取链表长度'''
        if self.is_empty():
            return 0
        count = 1
        cur = self.__head
        while cur.next != self.__head:
            count += 1
            cur = cur.next
        return count

    def travel(self):
        '''遍历链表'''
        if self.is_empty():
            print("")
        cur = self.__head
        print(cur.value, end=" ")
        while cur.next != self.__head:
            cur = cur.next
            print(cur.value, end=" ")
        print()

    def add(self, item):
        '''链表头部添加'''
        node = LinkListNode(item)
        if self.is_empty():
            node.prev = node
            node.next = node
            self.__head = node
        else:
            cur = self.__head
            node.prev = cur.prev
            node.next = cur
            cur.prev.next = node
            cur.prev = node
            self.__head = node

    def append(self, item):
        '''链表尾部添加'''
        node = LinkListNode(item)
        if self.is_empty():
            self.add(item)
        else:
            cur = self.__head
            node.prev = cur.prev
            node.next = cur
            cur.prev.next = node
            cur.prev = node

    def insert(self, pos, item):
        '''指定位置插入'''
        if pos <= 0:
            self.add(item)
        elif pos > (self.length() - 1):
            self.append(item)
        else:
            cur = self.__head
            count = 0
            while count < (pos - 1):
                count += 1
                cur = cur.next
            node = LinkListNode(item)
            node.prev = cur
            node.next = cur.next
            cur.next.prev = node
            cur.next = node

    def remove(self, item):
        '''删除节点'''
        cur = self.__head
        if self.is_empty():
            return print("链表为空")
        elif self.length() == 1:
            self.__head = None
        else:
            while cur.next != self.__head:
                if cur.value == item:
                    if cur == self.__head:
                        self.__head = cur.next
                        cur.next.prev = cur.prev
                        cur.prev.next = cur.next
                    else:
                        cur.next.prev = cur.prev
                        cur.prev.next = cur.next
                    return
                cur = cur.next
            if cur.value == item:
                cur.next.prev = cur.prev
                cur.prev.next = cur.next

    def search(self, item):
        '''查找节点是否存在'''
        if self.is_empty():
            return False
        cur = self.__head
        while cur.next != self.__head:
            if cur.value == item:
                return True
            cur = cur.next
        if cur.value == item:
            return True
        return False


if __name__ == "__main__":
    ll = DoubleLoopLinkList()
    ll.add(1)
    ll.add(2)
    ll.travel()
    ll.append(3)
    ll.travel()
    ll.insert(2, 4)
    ll.travel()
    ll.insert(4, 5)
    ll.travel()
    ll.insert(0, 6)
    ll.travel()
    print("length:", ll.length())
    ll.travel()
    print(ll.search(3))
    print(ll.search(7))
    ll.remove(1)
    ll.remove(2)
    # ll.remove(5)
    # ll.remove(4)
    # ll.remove(3)
    ll.remove(6)
    ll.travel()
    print("length:", ll.length())
    # ll.travel()