Python——栈、队列、链表的实现

栈

栈（stack），也称堆栈，是一种容器，特点是在于只能允许在容器的一段进行加入数据和输出数据的运算。
由于栈数据结构只允许在一端进行操作，因而按照后进先出（LIFO，Last In First Out）的原理运作

在这里插入代码片class Stack(object):
    '''栈'''
    def __init__(self):
        self.__list = []
    def push(self, item):
        '''添加一个新的元素item到栈顶'''
        self.__list.append(item)
    def pop(self):
        '''弹出栈顶元素'''
        return self.__list.pop()
    def peck(self):
        '''返回栈顶元素'''
        if self.__list:
            return self.__list[-1]
        else:
            return None
    def is_empty(self):
        '''判断栈是否为空'''
        return self.__list == []
    def size(self):
        '''返回栈的元素个数'''
        return len(self.__list)
if __name__ == '__main__':
    s = Stack()
    s.push(1)
    s.push(2)
    s.push(3)
    s.push(4)
    print(s.pop())
    print(s.pop())
    print(s.pop())
    print(s.pop())

队列

普通队列

队列（queue）是只允许在一端进行插入操作，而在另一端进行删除操作的线性表
队列是一种先进先出（First In First Out）的线性表，简称FIFO

class Queue(object):

    def __init__(self):
        self.__list = []

    #添加元素
    def inqueue(self, item):
        self.__list.append(item)

    #从队列头部取出一个元素
    def outqueue(self):
        return self.__list.pop(0)

    #判断队列是否为空
    def is_empty(self, item):
        return self.__list == []

    #返回队列的大小
    def size(self):
        return len(self.__list)

if __name__ == '__main__':
    s = Queue()
    s.inqueue(1)
    s.inqueue(2)
    s.inqueue(3)
    s.inqueue(4)
    print(s.outqueue())
    print(s.outqueue())
    print(s.outqueue())
    print(s.outqueue())

双端队列

class DoubleQueue(object):

    def __init__(self):
        self.__list = []

    def look_data(self):
        item = self.__list
        return item
    #从头部添加元素
    def add_front(self, item):
        self.__list.insert(0, item)

    # 从尾部添加元素
    def add_last(self, item):
        self.__list.append(item)
    #从队列头部取出一个元素

    #从头部取出元素
    def pop_front(self):
        return self.__list.pop(0)

    # 从尾部取出元素
    def pop_last(self):
        return self.__list.pop()

    #判断队列是否为空
    def is_empty(self, item):
        return self.__list == []

    #返回队列的大小
    def size(self):
        return len(self.__list)

if __name__ == '__main__':
    s = DoubleQueue()
    for i in range(0,5):
        s.add_front(i)
    for i in range(0,5):
        s.add_last(i)
    print(s.look_data())

    print(s.size())
    # for i in range(0,7):
    #     print(s.pop_front())
    for i in range(0,7):
        print(s.pop_last())

链表的实现

单向链表

class Node(object):
    def __init__(self, elem):
        self.elem = elem
        self.next = None
class SingLelinklist(object):
    def __init__(self, node=None):
        self.__head = node

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

    #链表长度
    def length(self):
        # cur游标，用来移动遍历节点
        cur = self.__head
        # count记录数量
        count = 0
        while cur != None:
            count += 1
            cur = cur.next
        return count

    #遍历链表
    def travel(self):
        cur = self.__head
        while cur != None:
            print(cur.elem, end=' ')
            cur = cur.next
        print('')

    #头插法
    def add(self, item):
        node = Node(item)
        node.next = self.__head
        self.__head = node

    #尾插法
    def append(self, item):
        node = Node(item)
        if self.is_empty():
            self.__head = node
        else:
            cur = self.__head
            while cur.next != None:
                cur = cur.next
            cur.next = node

    #指定位置添加元素
    def insert(self, pos, item):
        #pos从0开始
        if pos <= 0:
            self.add(item)
        elif pos > (self.length()-1):
            self.append(item)
        else:
            pre = self.__head
            count = 0
            while count < (pos-1):
                count += 1
                pre = pre.next
            #当循环退出后，pre只想pos-1位置
            node = Node(item)
            node.next = pre.next
            pre.next = node


    #删除节点
    def remove(self, item):
        cur = self.__head
        pre = None
        while cur != None:
            if cur.elem == item:
                #判断此节点是不是头结点
                if  cur == self.__head:
                    self.__head = cur.next
                else:
                    pre.next = cur.next
                break
            else:
                pre = cur
                cur = cur.next

    #查找节点是否存在
    def search(self, item):
        cur = self.__head
        while cur != None:
            if cur.elem == item:
                return True
            else:
                cur = cur.next
        return False

if __name__ == '__main__':
    ll = SingLelinklist()
    # print(ll.is_empty())
    # print(ll.length())

    ll.append(1)
    # print(ll.is_empty())
    # print(ll.length())

    ll.append(2)
    ll.add(8)
    ll.append(3)
    ll.append(4)
    ll.append(5)
    ll.append(6)
    ll.travel()
    ll.remove(8)
    ll.travel()
    ll.remove(6)
    ll.travel()

单向循环链表

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

        #单向循环列表
class SingLelinklist(object):
    def __init__(self, node=None):
        self.__head = node
        if node:
            node.next = node

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

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

    #遍历链表
    def travel(self):
        cur = self.__head
        while cur.next != self.__head:
            print(cur.elem, end=' ')
            cur = cur.next
        #退出循环，cur指向尾节点，但不没有打印
        print(cur.elem)
    #头插法
    def add(self, item):
        node = Node(item)
        cur = self.__head
        if self.is_empty():
            self.__head = node
            node.next = node
        while cur.next != self.__head:
            cur = cur.next
        # 退出循环，cur指向尾节点
        node.next = self.__head
        self.__head = node
        # cur.next = node
        cur.next = self.__head

    #尾插法
    def append(self, item):
        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

    #指定位置添加元素
    def insert(self, pos, item):
        #pos从0开始
        if pos <= 0:
            self.add(item)
        elif pos > (self.length()-1):
            self.append(item)
        else:
            pre = self.__head
            count = 0
            while count < (pos-1):
                count += 1
                pre = pre.next
            #当循环退出后，pre只想pos-1位置
            node = Node(item)
            node.next = pre.next
            pre.next = node


    #删除节点
    def remove(self, item):
        cur = self.__head
        pre = None
        if self.is_empty():
            return
        while cur.next != self.__head:
            if cur.elem == item:
                #判断此节点是不是头结点
                if  cur == self.__head:
                    #头结点
                    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，cur指向尾节点
        if cur.elem == item:
            if cur == self.__head:
                #链表只有一个节点
                self.__head = None
            else:
                pre.next = cur.next
    #查找节点是否存在
    def search(self, item):
        cur = self.__head
        if self.is_empty():
            return False
        while cur.next != self.__head:
            if cur.elem == item:
                return True
            else:
                cur = cur.next
        #退出循环，cur指向尾节点
        if cur.elem == item:
            return True
        return False

if __name__ == '__main__':
    ll = SingLelinklist()
    # print(ll.is_empty())
    # print(ll.length())

    ll.append(1)
    # print(ll.is_empty())
    # print(ll.length())

    ll.append(2)
    ll.add(8)
    ll.append(3)
    ll.append(4)
    ll.append(5)
    ll.append(6)
    ll.travel()
    ll.remove(8)
    ll.travel()
    ll.remove(6)
    ll.travel()

数据结构学习网址：https://www.bilibili.com/video/BV18W411T7Vv?p=1