python——python 数据结构之双向链表的实现

和单链表类似，只不过是增加了一个指向前面一个元素的指针而已。

示意图：

python 实现代码：

#Personal Python Data Structure--PPDS
#
#!/usr/bin/python
# -*- coding: utf-8 -*-
class Node(object):


    def __init__(self,val,p=0):
        self.data = val
        self.next = p
        self.prev = p

class LinkList(object):


    def __init__(self):
        self.head = 0

    def initlist(self,data):
        self.head = Node(data[0])
        p = self.head
        for i in data[1:]:
            node = Node(i)
            p.next = node
            node.prev = p
            p = p.next

    def getlength(self):
        length = 0
        p =  self.head
        while p != 0:
            length+=1
            p = p.next
        return length

    def is_empty(self):
        if self.getlength() == 0:
            return True
        else:
            return False

    def clear(self):
        self.head = 0

    def append(self,item):
        q = Node(item)
        if self.head == 0:
            self.head = q
        else:
            p = self.head
            while p.next != 0:
                p = p.next
            p.next = q
            q.prev = p

    def getitem(self,index):
        if self.is_empty():
            print ('Linklist is empty.')
            return
        j = 0
        p = self.head
        while p.next != 0 and j < index:
            p = p.next
            j+=1
        if j == index:
            return p.data
        else:
            print ('target is not exist!')

    def insert(self,index,item):
        if self.is_empty() or index < 0 or index > self.getlength():
            print ('Linklist is empty.')
            return
        if index == 0:
            q = Node(item,self.head)
            self.head = q
        j = 0        
        p = self.head
        post  = self.head
        while p.next != 0 and j < index:
            post = p
            p = p.next
            j+=1
        if index == j:
            q = Node(item,p)
            post.next = q
            q.prev = post
            q.next = p
            p.prev = q

    def delete(self,index):
        if self.is_empty() or index < 0 or index > self.getlength():
            print ('Linklist is empty.')
            return
        if index ==0:
            q = Node(item,self.head)
            self.head = q
        j = 0        
        p = self.head
        post  = self.head
        while p.next != 0 and j < index:
            post = p
            p = p.next
            j+=1
        if index ==j:
            post.next = p.next
            p.next.prev = post
            
    def index(self,value):
        if self.is_empty():
            print ('Linklist is empty.')
            return
        i = 0
        p = self.head
        while p.next != 0 and not p.data == value:
            p = p.next
            i+=1
        if p.data == value:
            return i
        else:
            return -1

if __name__ == '__main__':
    l=LinkList()
    llist=[7,3,10,4,5,]
    l.initlist(llist)

    print(l.getlength())
    print(l.is_empty())

    # l.append(11)
    # l.insert(2,100)

    print(l.getlength())
    print(l.getitem(0))
    for i in range(l.getlength()):
        print(l.index(llist[i]))
    l.clear()
    print(l.getlength())