python基本数据结构栈stack和队列queue

1，栈，后进先出，多用于反转

Python里面实现栈，就是把list包装成一个类，再添加一些方法作为栈的基本操作。

栈的实现：

class Stack(object):
    #初始化栈为空列表
    def __init__(self):
        self.items = []    #self.__items = []可以把items变成私有属性

    #判断栈是不是为空
    def isEmpty(self):
        return len(self.items) ==0

    #返回栈顶的元素
    def peek(self):
        return self.items[-1]

    #返回栈的大小
    def size(self):
        return len(self.items)

    #给栈加入新元素
    def push(self,a):
        self.items.append(a)

    #删除栈顶的元素
    def pop(self):
        return self.items.pop()

栈应用实例：十进制转化为二进制

def divideBy2(decNumber):
    remstack = Stack()    #实例化一个栈，因为需要栈结构来存储数据，也是为了用到栈方法

    while decNumber > 0:
        rem = decNumber%2    #除二倒取余法，最后反转拼接所有的余数
        remstack.push(rem)    #余数依次放到栈中储存起来
        decNumber = decNumber // 2

    binstring = ''
    while not remstack.is_empty():
        binstring = binstring + str(remstack.pop())    #反序获取栈中的元素

    return binstring

print divideBy2(10)

2 队列queue

队列实际上就是一个包装了的列表，从list[0]添加新元素，用pop()来获取，符合先进先出的规则。

class Queue:
    def __init__(self):
        self.items = []

    def isEmpty(self):
        return self.items == []

    def enqueue(self,item):    #添加一个新元素item到队列的开头，这叫队尾
        self.items.insert(0,item)

    def dequeue(self):    #减去一个最后一个元素，这叫队首
        return self.items.pop()

    def size(self):
        return len(self.items)

    def show(self):    #自主添加的，好跟踪查看队列里有啥
        return self.items

队列应用实例：热土豆

#就是一队人围着圈报数，从0开始，报到m就出局，看谁活最久。
from pythonds.basic.queue import Queue

def HotPotato(namelist,num):
    simqueue =  Queue()
    for name in namelist:
        simqueue.enqueue(name)    #把先namelist添加到队列中去，ps：从下标是0的位置开始添加，整个插入完成以后序列就反过来了
    while simqueue.size()>1:
        for i in range(num):    #
            simqueue.enqueue(simqueue.dequeue())
            #从列表的末尾减去什么就把什么添加到列表开头
        simqueue.dequeue()    #哪个排最后哪个就是热土豆，直接出局
    return simqueue.dequeue()

print  HotPotato(['lili','jiajia','dahu','wangba','daqing','tamato','potato','hehe'],3)

3 双端队列有点类似于列表，不多赘述

4，链表

基本链表的实现：    #链表是环环相扣形成的序列结构，每一环首先定义self变量，其次要标记下一个变量。所以访问的时候只能按照顺序来。

class Node:
    def __init__(self,initdata):
        self.data = initdata
        self.next = None

    def getData(self):
        return self.data

    def getNext(self):
        return self.next

    def setData(self,newdata):
        self.data = newdata

    def setNext(self,newnext):
        self.next = newnext

无序链表：

class UnorderedList:

    def __init__(self):
        self.head = None    #表示链表的头部不引用任何内容

    def isEmpty(self):
        return self.head == None

    def add(self,item):    #链表中有两个属性，一个是本身，一个是next，
        temp = Node(item)    #这个设定了链表本身，也就是data,无序链表也是由node构成的
        temp.setNext(self.head)    #这个设定了next
        self.head = temp    #把链表的data参数设定为无序列表的头----head

    def size(self):
        current = self.head
        count = 0
        while current != None:
            count = count +1
            current = current.getNext()
        return count

    def search(self,item):
        current = self.head
        found = False
        while current != None and not found:
            if current.getData() == item:
                found = True
            else:
                current = current.getNext()
            return found

    def remove(self,item):
        current = self.head
        previous=None
        found = False
        while not found:    #找到要删除的item以后会跳出循环，此时current.getData()是要删除的项目
            if current.getData()==item:
                found=True
            else:
                previous=current
                current=current.getNext()
        if previous ==None:    #只有一种情况下，previous会是None，那就是要删除的是第一个，也就是想删除self.head
            self.head=current.getNext()
        else:
            previous.setNext(current.getNext())    # 本来的指向是previous.getData()--item(也就是previous.getNext(),还是current.getData())--current.getNext()
                                                   #要想删除item，那就把previous的指向改成current.getNext()，这样item就不能在原来的链表中瞎掺和了 

有序链表：

class OrderedList:
    def __init__(self):
        self.head = None

    def isEmpty(self):    #同无序列表
        return self.head == None

    def show(self):
        current = self.head
        while current != None:
            print current.getData()
            current = current.getNext()

    def __iter__(self):
        current = self.head
        while current != None:
            yield current.getData()
            current = current.getNext()

    def size(self):    #同无序列表
        current = self.head
        count = 0
        while current != None:
            count +=1
            current =current.getNext()
        return count

    def search(self,item):    #默认从小到大排列的链表
        current = self.head
        found = False
        stop = False
        while current != None and not found and not stop:
            if current.getData() == item:
                found = True
            else:
                if current.getData() > item:
                    stop = True
                else:
                    current = current.getNext()
        return found

    def add(self,item):
        current = self.head
        previous = None
        stop = False
        while current != None and not stop:    #有一个以上元素的情况
            if current.getData() > item:
                stop = True
            else:
                previous = current
                current = current.getNext()    #不用担心元素添加到最后的情况，因为链表中自带None封住了两头

        temp = Node(item)
        if previous == None:    #添加到链表头的情况
            temp.setNext(self.head)
            self.head=temp
        else:
            temp.setNext(current)
            previous.setNext(temp)

    def remove(self, item):
        current = self.head
        previous = None
        found = False
        while not found:
            # 迭代每一项，得到要删除的那个，并且通过赋值前一个执行删除
            if current.getData() == item:
                found = True
            else:
                previous = current
                current = current.getNext()
        if previous == None:
            # 如果删除的是第一项，那么把第二项变成第一项，否则给previous赋值
            self.head = current.getNext()
        else:
            previous.setNext(current.getNext())