編寫一個類，用兩個棧實(shí)現(xiàn)一個隊(duì)列，支持隊(duì)列的基本操作（add,poll,peek）

思路：棧的特點(diǎn)是先進(jìn)后出，隊(duì)列的特點(diǎn)是先進(jìn)先出，具體實(shí)現(xiàn)是一個棧作為壓入棧，在壓入數(shù)據(jù)時只往這個棧中壓入，記為stackPush,另一個棧只作為彈出棧，在彈出數(shù)據(jù)時只從這個棧彈出，記為stackPop

注意需要滿足兩點(diǎn):

1、如果stackPush要往stackPop壓入數(shù)據(jù)時，stackPop的棧必須為空

2、從stackPush往stackPop壓入數(shù)據(jù)時，必須一次把stackPush所有數(shù)據(jù)一次性全部壓入

class Stack():def __init__(self):self.item = []def pop(self):if len(self.item)==0:return "the Stack is empty"else:self.item.pop()def push(self,item):self.item.append(item)def peek(self):return self.item[len(self.item)-1]def isEmpty(self):if len(self.item)==0:return Truereturn Falseclass MyStack():def __init__(self):self.stackPush = Stack()self.stackPop = Stack()def pushTopPop():if self.stackPop.isEmpty:while self.stackPush.isEmpty is not True:self.stackPop.push(self.stackPush.pop())def add(num):self.stackPush(num)self.pushToPop()def poll():if self.stackPop.empty() and self.stackPush.empty():return "queue is empty"self.pushToPop()return self.stackPop.pop()def peek():if self.stackPop.empty() and self.stackPush.empty():return "Queue is empty"self.pushToPop()return stackPop.peek()

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由兩個隊(duì)列實(shí)現(xiàn)一個棧

思路：使用兩個隊(duì)列，第一個隊(duì)列彈出數(shù)，進(jìn)入第二個隊(duì)列，如果第一個隊(duì)列彈完剩下一個元素即最后一個元素，返回該值；之后調(diào)換兩個隊(duì)列的索引重復(fù)之前過程

class queue():def __init__(self,Size):self.item = []self.Size = Sizedef isEmpty(self):if len(self.item) == 0:return Truereturn Falsedef enqueue(self,item):if len(self.item) > self.Size:return "the queue is full"else:self.item.insert(0,item)def dequeue(self):if len(self.item) == 0:return "the queue is empty"else:return self.item.pop()class QueueToStack():def __init__(self):self.queue = queue()self.help = queue()def push(num):self.queue.enqueue(num)def peek():if self.queue.isEmpty():return "Stack is empty"while len(self.queue.item)!=1:self.help.enqueue(self.queue.dequeue())res = self.queue.dequeue() //最后一個數(shù) 切掉self.help.enqueue(res)self.swap()return resdef pop():if self.queue.isEmpty():return "Stack is empty"while len(self.queue.item)>1:self.help.enqueue(self.queue.dequeue())res = self.queue.dequeue()self.swap()return resdef swap():tmp = self.helpself.help = self.queueself.queue = tmp

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