Python实现链表

单链表：

# -*- coding:utf-8 -*-
class node(object):
    """节点"""
    def __init__(self,elem):
        self.elem = elem
        self.next = None

class SingleLinkList(object):
    """单链表"""
    #头结点
    def __init__(self,node = None):
        self._head = node
    def is_empty(self):
        if self._head == None:
            return True
        else :
            return False
    def length(self):
        cur = self._head
        count = 0
        while cur != None:
            cur = cur.next
            count += 1
        return count
    def travel(self):
        """遍历整个链表"""
        cur = self._head
        if cur == None:
            return
        count = 0
        while cur != None:
            print(cur.elem,end=" ")
            cur = cur.next
            count += 1
        return count
    def add(self,item):
        """链表头部添加元素"""
        node =Node(item)
        node.next = self._head
        self._head = node
    def append(self,item):
        """链表尾部添加元素,叫尾插法"""
        node = Node(item)
        if self.is_empty():
            self._head = node
        else:
            cur = self._head
            while cur.next !=None:
                cur = cur.next
            cur.next = node
    def insert(self,pos,item):
        """指定位置添加元素
        :param pos 从0开始
        """
        if pos <= 0:
            self.add(item)
        elif pos >= self.length():
            self.append(item)
        else :
            pre = self._head
            count = 0
            while count <= pos -1:
                pre = pre.next
                count += 1
            node = Node(item)
            node.next = pre.next
            pre.next = node
    def remove(self,item):
        """删除指定的节点"""
        cur = self._head
        pre = None
        while cur != None:
            if cur.elem == item:
                #判断是否为头结点
                if cur == self._head:
                    self._head = cur.next
                    break
                else :
                    pre.next = cur.next
                    break
            else :
                pre = cur
                cur = cur.next
    def search(self,item):
        """查找节点是否存在"""
        cur = self._head
        while cur != None:
            if cur.elem == item:
                return  True
            else :
                cur = cur.next
        return False

if __name__ == "__main__":
    single_obj = SingleLinkList()
    print(single_obj.is_empty())     #True

        print(single_obj.length())        #0
    single_obj.append(1)
    print(single_obj.is_empty())
    print(single_obj.length())

    single_obj.append(2)
    single_obj.add(8)
    single_obj.append(3)
    single_obj.append(4)
    single_obj.append(5)
    single_obj.append(6)
    single_obj.travel()       #8 1 2 3 4 5 6
    print(" ")
    single_obj.insert(-1,9)
    single_obj.travel()       #9 8 1 2 3 4 5 6
    print(" ")
    single_obj.insert(5,100)
    single_obj.travel()       #9 8 1 2 3 4 100 5 6
    print(" ")
    single_obj.insert(10,200)
    single_obj.travel()       #9 8 1 2 3 4 100 5 6 200
    print(" ")
    single_obj.remove(200)
    single_obj.travel()       # 9 8 1 2 3 4 100 5 6

双向链表：

# -*- coding:utf-8 -*-
class Node(object):
    """节点"""
    def __init__(self,item):
        self.elem = item
        self.prev = None
        self.next = None

class Double_linked_list(object):
    """双链表"""
    def __init__(self,node = None):
        self._head = node
    def is_empty(self):
        if self._head is None:
            return True
        else:
            return False
    def length(self):
        cur = self._head
        count = 0
        while cur != None:
            cur = cur.next
            count += 1
        return count
    def travel(self):
        """遍历整个链表"""
        cur = self._head
        if cur == None:
            return
        count = 0
        while cur != None:
            print(cur.elem,end=" ")
            cur = cur.next
            count += 1
        return count
    def add(self,item):
        """链表头部添加元素"""
        node =Node(item)
        node.next = self._head
        self._head = node
        node.next.prev = node
    def append(self,item):
        """链表尾部添加元素,叫尾插法"""
        node = Node(item)
        if self.is_empty():
            self._head = node
        else:
            cur = self._head
            while cur.next !=None:
                cur = cur.next
            cur.next = node
            node.prev = cur
    def insert(self,pos,item):
        """指定位置添加元素
        :param pos 从0开始
        """
        if pos <= 0:
            self.add(item)
        elif pos >= self.length():
            self.append(item)
        else :
            cur = self._head
            count = 0
            while count < pos :
                cur = cur.next
                count += 1
            node = Node(item)
            node.next = cur
            node.prev = cur.prev
            cur.prev.next = node
            cur.prev = node
    def remove(self,item):
        """删除指定的节点"""
        cur = self._head
        while cur != None:
            if cur.elem == item:
                #判断是否为头结点
                if cur == self._head:
                    self._head = cur.next
                    if cur.next:
                        #判断链表是否只有一个节点
                        cur.next.prev = None
                    break
                else :
                    cur.prev.next = cur.next
                    if cur.next:
                        cur.next.prev = cur.prev
                    break
            else :
                pre = cur
                cur = cur.next
    def search(self,item):
        """查找节点是否存在"""
        cur = self._head
        while cur != None:
            if cur.elem == item:
                return  True
            else :
                cur = cur.next
        return False

if __name__ == "__main__":
    linkl = Double_linked_list()
    print(linkl.is_empty())
    print(linkl.length())

    linkl.append(1)
    print(linkl.is_empty())
    print(linkl.length())

    linkl.append(2)
    linkl.add(8)
    linkl.append(3)
    linkl.append(4)
    linkl.append(5)
    linkl.append(6)
    linkl.travel()       #8 1 2 3 4 5 6
    print(" ")
    linkl.insert(-1,9)
    linkl.travel()       #9 8 1 2 3 4 5 6
    print(" ")
    linkl.insert(5,100)
    linkl.travel()       #9 8 1 2 3 4 100 5 6
    print(" ")
    linkl.insert(10,200)
    linkl.travel()       #9 8 1 2 3 4 100 5 6 200
    print(" ")
    linkl.remove(200)
    linkl.travel()       # 9 8 1 2 3 4 100 5 6