数据结构：队列 链表，顺序表和循环顺序表实现（python版）

#!/usr/bin/env python
# -*- coding:utf-8 -*- class QueueUnderflow(ValueError):
pass #链表节点
class Node(object):
def __init__(self, elem, next_ = None):
self.elem = elem
self.next = next_ #链表实现队列,头部删除和查看O(1),尾部加入O(1)
class LQueue(object):
def __init__(self):
self._head = None
self._rear = None def is_empty(self):
return self._head is None #查看队列中最早进入的元素，不删除
def peek(self):
if self.is_empty():
raise QueueUnderflow
return self._head.elem #将元素elem加入队列，入队
def enqueue(self, elem):
p = Node(elem)
if self.is_empty():
self._head = p
self._rear = p
else:
self._rear.next = p
self._rear =p #删除队列中最早进入的元素并将其返回，出队
def dequeue(self):
if self.is_empty():
raise QueueUnderflow
result = self._head.elem
self._head = self._head.next
return result #顺序表实现队列,头部删除和查看O(1),尾部加入O(n)
class Simple_SQueue(object):
def __init__(self, init_len = 8):
self._len = init_len
self._elems = [None] * init_len
self._num = 0 def is_empty(self):
return self._num == 0 def is_full(self):
return self._num == self._len def peek(self):
if self._num == 0:
raise QueueUnderflow
return self._elems[self._num-1] def dequeue(self):
if self._num == 0:
raise QueueUnderflow
result = self._elems[self._num-1]
self._num -= 1
return result def enqueue(self,elem):
if self.is_full():
self.__extand()
for i in range(self._num,0,-1):
self._elems[i] = self._elems[i-1]
self._elems[0] = elem
self._num += 1 def __extand(self):
old_len = self._len
self._len *= 2
new_elems = [None] * self._len
for i in range(old_len):
new_elems[i] = self._elems[i]
self._elems = new_elems #循环顺序表实现队列,头部删除和查看O(1),尾部加入O(1)
class SQueue(object):
def __init__(self, init_num = 8):
self._len = init_num
self._elems = [None] * init_num
self._head = 0
self._num = 0 def is_empty(self):
return self._num == 0 def peek(self):
if self.is_empty():
raise QueueUnderflow
return self._elems[self._head] def dequeue(self):
if self.is_empty():
raise QueueUnderflow
result = self._elems[self._head]
self._head = (self._head + 1) % self._len
self._num -= 1
return result def enqueue(self, elem):
if self._num == self._len:
self.__extand()
self._elems[(self._head + self._num) % self._len] = elem
self._num += 1 def __extand(self):
old_len = self._len
self._len *= 2
new_elems = [None] * self._len
for i in range(old_len):
new_elems[i] = self._elems[(self._head + i) % old_len]
self._elems, self._head = new_elems, 0 if __name__=="__main__":
q = SQueue()
for i in range(8):
q.enqueue(i)
#for i in range(8):
# print(q.dequeue())
#print(q._num)
q.enqueue(8)
print(q._len)