Python——棧、隊列、鏈表的實現

棧

棧（stack），也稱堆棧，是一種容器，特點是在於只能允許在容器的一段進行加入數據和輸出數據的運算。
由於棧數據結構只允許在一端進行操作，因而按照後進先出（LIFO，Last In First Out）的原理運作

在這裏插入代碼片class Stack(object):
    '''棧'''
    def __init__(self):
        self.__list = []
    def push(self, item):
        '''添加一個新的元素item到棧頂'''
        self.__list.append(item)
    def pop(self):
        '''彈出棧頂元素'''
        return self.__list.pop()
    def peck(self):
        '''返回棧頂元素'''
        if self.__list:
            return self.__list[-1]
        else:
            return None
    def is_empty(self):
        '''判斷棧是否爲空'''
        return self.__list == []
    def size(self):
        '''返回棧的元素個數'''
        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())

隊列

普通隊列

隊列（queue）是隻允許在一端進行插入操作，而在另一端進行刪除操作的線性表
隊列是一種先進先出（First In First Out）的線性表，簡稱FIFO

class Queue(object):

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

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

    #從隊列頭部取出一個元素
    def outqueue(self):
        return self.__list.pop(0)

    #判斷隊列是否爲空
    def is_empty(self, item):
        return self.__list == []

    #返回隊列的大小
    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())

雙端隊列

class DoubleQueue(object):

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

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

    # 從尾部添加元素
    def add_last(self, item):
        self.__list.append(item)
    #從隊列頭部取出一個元素

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

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

    #判斷隊列是否爲空
    def is_empty(self, item):
        return self.__list == []

    #返回隊列的大小
    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())

鏈表的實現

單向鏈表

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

    #判斷鏈表是否爲空
    def is_empty(self):
        return self.__head == None

    #鏈表長度
    def length(self):
        # cur遊標，用來移動遍歷節點
        cur = self.__head
        # count記錄數量
        count = 0
        while cur != None:
            count += 1
            cur = cur.next
        return count

    #遍歷鏈表
    def travel(self):
        cur = self.__head
        while cur != None:
            print(cur.elem, end=' ')
            cur = cur.next
        print('')

    #頭插法
    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從0開始
        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
            #當循環退出後，pre只想pos-1位置
            node = Node(item)
            node.next = pre.next
            pre.next = node


    #刪除節點
    def remove(self, item):
        cur = self.__head
        pre = None
        while cur != None:
            if cur.elem == item:
                #判斷此節點是不是頭結點
                if  cur == self.__head:
                    self.__head = cur.next
                else:
                    pre.next = cur.next
                break
            else:
                pre = cur
                cur = cur.next

    #查找節點是否存在
    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()

單向循環鏈表

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

        #單向循環列表
class SingLelinklist(object):
    def __init__(self, node=None):
        self.__head = node
        if node:
            node.next = node

    #判斷鏈表是否爲空
    def is_empty(self):
        return self.__head == None

    #鏈表長度
    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

    #遍歷鏈表
    def travel(self):
        cur = self.__head
        while cur.next != self.__head:
            print(cur.elem, end=' ')
            cur = cur.next
        #退出循環，cur指向尾節點，但不沒有打印
        print(cur.elem)
    #頭插法
    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
        # 退出循環，cur指向尾節點
        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從0開始
        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
            #當循環退出後，pre只想pos-1位置
            node = Node(item)
            node.next = pre.next
            pre.next = node


    #刪除節點
    def remove(self, item):
        cur = self.__head
        pre = None
        if self.is_empty():
            return
        while cur.next != self.__head:
            if cur.elem == item:
                #判斷此節點是不是頭結點
                if  cur == self.__head:
                    #頭結點
                    rear = self.__head
                    while rear.next != self.__head:
                        rear = rear.next
                    self.__head = cur.next
                    rear.next = self.__head
                    #中間節點
                else:
                    pre.next = cur.next
                return
            else:
                pre = cur
                cur = cur.next
        #退出循環，cur指向尾節點
        if cur.elem == item:
            if cur == self.__head:
                #鏈表只有一個節點
                self.__head = None
            else:
                pre.next = cur.next
    #查找節點是否存在
    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
        #退出循環，cur指向尾節點
        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()

數據結構學習網址：https://www.bilibili.com/video/BV18W411T7Vv?p=1