从生活中,能够抽象出队列的概念,队列就是一个能够实现“先进先出”的存储结构。队列分为链式队列和静态队列;静态队列一般用数组来实现,但此时的队列必须是循环队列,否则会造成巨大的内存浪费;链式队列是用链表来实现队列的。这里讲的是循环队列,首先我们必须明确以下几个问题
一、循环队列的基础知识
1.循环队列须要几个參数来确定
循环队列须要2个參数,front和rear
2.循环队列各个參数的含义
(1)队列初始化时,front和rear值都为零;
(2)当队列不为空时,front指向队列的第一个元素,rear指向队列最后一个元素的下一个位置;
(3)当队列为空时,front与rear的值相等,但不一定为零;
Code:
1:class MyCircularQueue:
def __init__(self, k):
"""
Initialize your data structure here. Set the size of the queue to be k.
:type k: int
"""
self.size = k+1
self.data = [0]*self.size
self.head = self.rear = 0
def enQueue(self, value):
"""
Insert an element into the circular queue. Return true if the operation is successful.
:type value: int
:rtype: bool
"""
if self.isFull():
return False
self.data[self.rear] = value
self.rear = (self.rear+1)%self.size
return True
def deQueue(self):
"""
Delete an element from the circular queue. Return true if the operation is successful.
:rtype: bool
"""
if self.isEmpty():
return False
self.head = (self.head+1)%self.size
return True
def Front(self):
"""
Get the front item from the queue.
:rtype: int
"""
if self.isEmpty():
return -1
return self.data[self.head]
def Rear(self):
"""
Get the last item from the queue.
:rtype: int
"""
if self.isEmpty():
return -1
return self.data[(self.rear-1)%self.size]
def isEmpty(self):
"""
Checks whether the circular queue is empty or not.
:rtype: bool
"""
return self.head ==self.rear
def isFull(self):
"""
Checks whether the circular queue is full or not.
:rtype: bool
"""
return (self.rear+1)%self.size ==self.head
2.增加一个变量记录队列的长度
class MyCircularQueue:
def __init__(self, k):
"""
Initialize your data structure here. Set the size of the queue to be k.
:type k: int
"""
self.queue = [0] * k
self.head = 0
self.tail = 0
self.lenth = k
self.count = 0
def enQueue(self, value):
"""
Insert an element into the circular queue. Return true if the operation is successful.
:type value: int
:rtype: bool
"""
if self.count < self.lenth:
self.queue[self.tail] = value
self.tail = (self.tail + 1) % self.lenth
self.count += 1
return True
else:
return False
def deQueue(self):
"""
Delete an element from the circular queue. Return true if the operation is successful.
:rtype: bool
"""
if self.count > 0:
self.queue[self.head] = 0
self.head = (self.head + 1) % self.lenth
self.count -= 1
return True
else:
return False
def Front(self):
"""
Get the front item from the queue.
:rtype: int
"""
if self.count > 0:
return self.queue[self.head]
else:
return -1
def Rear(self):
"""
Get the last item from the queue.
:rtype: int
"""
if self.count > 0:
return self.queue[(self.tail + self.lenth - 1) % self.lenth]
else:
return -1
def isEmpty(self):
"""
Checks whether the circular queue is empty or not.
:rtype: bool
"""
if self.count == 0:
return True
else:
return False
def isFull(self):
"""
Checks whether the circular queue is full or not.
:rtype: bool
"""
if self.count == self.lenth:
return True
else:
return False