python数据结构之单链表的实现

python数据结构之单链表的实现

单向链表
单向链表也叫单链表，是链表中最简单的一种形式，它的每个节点包含两个域，一个信息域（元素域）和一个链接域。这个链接指向链表中的下一个节点，而最后一个节点的链接域则指向一个空值。

单向链表图示：

表元素域elem用来存放具体的数据。
链接域next用来存放下一个节点的位置（python中的标识）
变量p指向链表的头节点（首节点）的位置，从p出发能找到表中的任意节点。

class Node(object):
    """节点"""
    def __init__(self, elem):
        self.elem = elem
        self.next = None


class SingleLinkList(object):

    def __init__(self, node=None):
        """初始化"""
        self.__head = node

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

    def length(self):
        """链表长度"""
        current_node = self.__head
        count = 0
        while current_node is not None:
            count += 1
            current_node = current_node.next
        return count

    def travel(self):
        """遍历链表"""
        current_node = self.__head
        while current_node is not None:
            print(current_node.elem, end=' ')
            current_node = current_node.next
        print('')

    def add(self, item):
        """链表头部添加元素， 头插法"""
        node = Node(item)
        current_node = self.__head
        node.next = current_node
        self.__head = node

    def append(self, item):
        """链表尾部添加元素, 尾插法"""
        node = Node(item)
        if self.is_empty():
            self.__head = node
        else:
            current_node = self.__head
            while current_node.next is not None:
                current_node = current_node.next
            current_node.next = node

    def search(self, item):
        """查找节点"""
        current_node = self.__head
        while current_node is not None:
            elem = current_node.elem
            if elem == item:
                return True
            current_node = current_node.next
        return False

    def insert(self, index, item):
        """指定位置插入节点"""
        if index <= 0:
            self.add(item)
        elif index >= self.length():
            self.append(item)
        else:
            current_node = self.__head
            while index > 1:
                index -= 1
                current_node = current_node.next
            node = Node(item)
            node.next = current_node.next
            current_node.next = node

    def pop(self, index):
        """删除指定位置节点"""
        current_node = self.__head
        if current_node is not None:
            if index <= 1:  # 删除头结点
                self.__head = current_node.next
            elif index >= self.length():  # 删除尾节点
                count = self.length()
                while count > 2:
                    count -= 1
                    current_node = current_node.next
                current_node.next = None
            else:
                pre_node = None
                while index >= 2:
                    index -= 1
                    pre_node = current_node
                    current_node = current_node.next
                pre_node.next = current_node.next

    def remove(self, item):
        """删除特定值节点"""
        current_node = self.__head
        pre_node = None
        while current_node != None:
            if current_node.elem == item:
                # 先判断此结点是否是头节点
                # 头节点
                if current_node == self.__head:
                    self.__head = current_node.next
                else:
                    pre_node.next = current_node.next
                break
            else:
                pre_node = current_node
                current_node = current_node.next


if __name__ == '__main__':
    link_list = SingleLinkList()
    print(link_list.is_empty())
    print(link_list.length())
    link_list.travel()

    link_list.add(1)
    link_list.travel()
    link_list.add(2)
    print(link_list.length())
    print(link_list.is_empty())
    link_list.travel()

    link_list.append(3)
    link_list.travel()
    print(link_list.search(3))
    print(link_list.search(4))

    link_list.insert(1, 100)
    link_list.travel()
    link_list.insert(3, 300)
    link_list.travel()

    link_list.append(500)
    link_list.travel()
    link_list.pop(2)
    link_list.travel()

    link_list.remove(500)
    link_list.travel()