#!/usr/bin/env python

 # -*- coding:utf-8 -*-

 #Author: Minion-Xu

 #list实现优先队列

 class ListPriQueueValueError(ValueError):

     pass

 class List_Pri_Queue(object):

     def __init__(self, elems = []):

         self._elems = list(elems)

         #从大到小排序，末尾值最小，但优先级最高，方便弹出且效率为O（1）

         self._elems.sort(reverse=True)

     #判断队列是否为空

     def is_empty(self):

         return self._elems is []

     #查看最高优先级 O(1)

     def peek(self):

         if self.is_empty():

             raise ListPriQueueValueError("in pop")

         return self._elems[-1]

     #弹出最高优先级 O(1)

     def dequeue(self):

         if self.is_empty():

             raise ListPriQueueValueError("in pop")

         return self._elems.pop()

     #入队新的优先级 O(n)

     def enqueue(self, e):

         i = len(self._elems) - 1

         while i>=0:

             if self._elems[i] < e:

                 i -= 1

             else:

                 break

         self._elems.insert(i+1, e)

 if __name__=="__main__":

     l = List_Pri_Queue([4,6,1,3,9,7,2,8])

     print(l._elems)

     print(l.peek())

     l.dequeue()

     print(l._elems)

     l.enqueue(5)

     print(l._elems)

     l.enqueue(1)

     print(l._elems)