Python 实现链表及相关操作 （单链表 单循环链表 双循环链表）

1.单链表

• 引入游标 cur ，来遍历链表.

##定义节点
class Node(object):
    def __init__(self,item):
        self.elem = item
        self.next = None

##定义单链表
class SingleLinkList(object):
    ##设置保存头节点的内存，并且设置为私有字段，函数内部使用
    def __init__(self,node=None):
        self.__head = node

    ##判断链表是否为空
    def is_empty(self):
        return self.__head is None
    ##直接返回 为空返回True 否则返回False

    ##遍历
    def travel(self):
        '''引入一个游标cur,用来遍历'''
        cur = self.__head
        while cur != None:
            print(cur.elem, end=" ")
            cur = cur.next

	##链表长度
    def length(self):
        count = 0
        cur = self.__head
        while cur != None:
            count += 1
            cur = cur.next
        return count

    #头插法插入数据
    #item是要插入的数据
    def add(self,item):
        #成成节点
        node = Node(item)
        cur = self.__head
        #如果链表为空
        if self.__head == None:
            self.__head = node
            # cur.next = node
        else:
            node.next = self.__head
            self.__head = node

   ##尾插法
    def append(self,item):
        node = Node(item)
        if self.is_empty():
            ##如果链表为空
            self.__head = node
        else:
            ##找到最后一个节点
            cur = self.__head
            ##注意此处的循环条件，cur.next!=None
            while cur.next != None:
                cur = cur.next
            cur.next = node

    ##指定位置插入
    def insert(self,pos,item):
        node = Node(item)
        #pos代表指定插入位置，item代表数值
        if pos<=0:
            self.add(item)
        elif pos >= (self.length()-1):
            self.append(item)
        else:
            count = 0
            cur = self.__head
            while count < pos-1:
                cur = cur.next
                count += 1
            node.next = cur.next
            cur.next = node

    ##删除指定元素
    def remove(self,item):

        cur = self.__head
        ##引入cur的一个前节点
        pre = None
        while cur!= None:
            if cur.elem == item:
                if cur == self.__head:
                    self.__head = cur.next
                else:
                    pre.next = cur.next
                    break
            else:
                pre = cur
                cur = cur.next

    ##判断是否存在元素
    def search(self,item):
        cur = self.__head
        while cur != None:
            if cur.elem == item:
                return True
            else:
                cur = cur.next
        return False
##测试方法
if __name__ == '__main__':
    ll=SingleLinkList()
    print(ll.is_empty())
    print(ll.length())
    ll.add(5)
    ll.append(6)
    ll.insert(1,2)
    ll.travel()
    ll.remove(1)
    ll.travel()

2.单循环链表

##单列表
##把节点封装成一个类
class Node(object):
     def __init__(self,elem):
         self.elem = elem
         self.next = None
'''单链表'''
class SingleCycleLinkList(object):
    '''单向循环链表'''
    ##设置保存头节点的内存，并且保存为私有属性，仅函数内部使用
    def __init__(self,node=None):
        '''构造非空链表时，让其他域指向自己'''
        if node:
            node.next = node
        ##若为空的链表
        self._head = node

    def is_empty(self):
        ##判断指向是否为空
        return self._head == None

    def length(self):
        ##引入一个游标Cur,移动遍历元素
        if self.is_empty():
            return 0
        cur = self._head

        ##count记录数量,count从1开始计数
        count = 1
        while cur.next != self._head:
            count += 1
            cur = cur.next
        return count
        # cur = self._head
        # if cur == None:
        #     count = 0
        #     return count
        # else:
        #     count = 0
        #     while cur != None:
        #         count += 1
        #         cur = cur.next
        #     return  count

    def travel(self):
        if self.is_empty():
            return
        cur = self._head
        while cur.next !=self._head:
            print(cur.elem,end=' ')
            cur =cur.next
        ##退出循环时，尾节点没有被打印出来，所以手动打印一下
        print(cur.elem)


    def add(self,item):
        '''头插法'''
        node = Node(item)
        if self.is_empty():
            self._head=node
            node.next=node
        else:
            cur = self._head
            while cur.next != self._head:
                cur = cur.next
            node.next=self._head
            self._head = node
            cur.next=node

    def append(self,item):
        '''尾部插入,尾插法'''
        ##item指具体数据，不是节点数
        node = Node(item)
        if self.is_empty():
            self._head=node
            node.next=node
        else:
            cur = self._head
            while cur.next != self._head:
                cur = cur.next
            cur.next = node
            node.next=self._head

    def insert(self,pos,item):
        '''
        指定位置插入数据
        '''
        if pos < 0:
            self.add(item)
        elif pos > (self.length()-1):
            self.append()
        else:
            node = Node(item)
            pre = self._head
            count = 0
            while count < pos-1:
                pre = pre.next
                count += 1
            node.next = pre.next
            pre.next = node

    def remove(self,item):
        # if self.search(item):
        #     '''删除元素'''
        #     pre = self._head
        #     while pre.next.elem != item:
        #         pre = pre.next
        #     pre.next = pre.next.next
        if self.is_empty():
            return
        cur = self._head
        pre = None
        while cur.next != self._head:
            if cur.elem == item:
                ##判断此节点是否是头节点
                if cur == self._head:
                    ##找尾节点
                    rear = self._head
                    while rear.next != self._head:
                        rear=rear.next
                    self._head = cur.next
                    rear.next = self._head
                ##中间节点
                else:
                    pre.next = cur.next
                return
            else:
                pre = cur
                cur = cur.next
        ##退出循环 尾部节点
        if cur.elem == item:
            if cur == self._head:
                self._head = None
            pre.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.elem == item:
                return True
            else:
                cur = cur.next
        if cur.elem ==item :
            return True
        return False

3.双循环链表

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

class DoubleLinkList(object):
    '''双链表'''
    def __init__(self,node=None):
        self._head = None

    def is_empty(self):
        return  self._head is None

    def length(self):
        '''链表长度'''
        cur = self._head
        count = 0
        while cur != None:
            cur = cur.next
            count += 1
        return count
	
	##遍历
    def travel(self):
        cur = self._head
        while cur != None:
            print(cur.elem,end=" ")
        print("")
	
	##头插法
    def add(self,item):
        node = Node(item)
        node.next = self._head
        self._head = node
        node.next.prev = node
        return
	
	##尾插法
    def append(self,item):
        node = Node(item)
        cur = self._head
        while cur != None:
            cur = cur.next
        cur.next = node
        cur.next = node
        node.prev = cur
        return
	
	##指定位置插入
    def insert(self,pos,item):
        if pos <= 0:
            self.add(item)
        elif pos > (self.length()-1):
            self.append(item)
        else:
            count = 0
            cur = self._head
            while count < pos:
                cur =cur.next
            ##退出循环后，cur指向pos位置

            node = Node(item)

            node.next = cur
            node.prev = cur.prev
            cur.prev.next = node
            cur.prev = node
            # node.next=cur.next
            # cur.next=node
            # node.prev=cur
            # node.next.prev=node

	##删除
    def remove(self,item):
        '''删除'''
        cur = self._head
        while cur != None:
            if cur.elem == item:
                ##判断此节点是否为头节点
                if cur == self._head:
                    self._head = cur.next
                    if cur.next:
                        #判断是否只有一个节点
                        cur.next.prev=None
                else:
                    cur.prev.next=cur.next
                    if cur.next:
                        ##判断是否存在
                        cur.next.prev = cur.prev
            break
	##判断元素是否存在
    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