链表实现队列：
尾部 添加数据，效率为0(1)
头部 元素的删除和查看，效率也为0(1)
顺序表实现队列：
头部 添加数据，效率为0(n)
尾部 元素的删除和查看，效率也为0(1)
循环顺序表实现队列：
尾部 添加数据，效率为0(1)
头部 元素的删除和查看，效率也为0(1)
1 #!/usr/bin/env python
2 # -*- coding:utf-8 -*-
3
4 class QueueUnderflow(ValueError): 5 pass
6
7 #链表节点
8 class Node(object): 9 def __init__(self, elem, next_ = None): 10 self.elem = elem 11 self.next = next_ 12
13 #链表实现队列,头部删除和查看O(1),尾部加入O(1)
14 class LQueue(object): 15 def __init__(self): 16 self._head = None 17 self._rear = None 18
19 def is_empty(self): 20 return self._head is None 21
22 #查看队列中最早进入的元素，不删除
23 def peek(self): 24 if self.is_empty(): 25 raise QueueUnderflow 26 return self._head.elem 27
28 #将元素elem加入队列，入队
29 def enqueue(self, elem): 30 p = Node(elem) 31 if self.is_empty(): 32 self._head = p 33 self._rear = p 34 else: 35 self._rear.next = p 36 self._rear =p 37
38 #删除队列中最早进入的元素并将其返回，出队
39 def dequeue(self): 40 if self.is_empty(): 41 raise QueueUnderflow 42 result = self._head.elem 43 self._head = self._head.next 44 return result 45
46 #顺序表实现队列,头部删除和查看O(1),尾部加入O(n)
47 class Simple_SQueue(object): 48 def __init__(self, init_len = 8): 49 self._len = init_len 50 self._elems = [None] * init_len 51 self._num = 0 52
53 def is_empty(self): 54 return self._num == 0 55
56 def is_full(self): 57 return self._num == self._len 58
59 def peek(self): 60 if self._num == 0: 61 raise QueueUnderflow 62 return self._elems[self._num-1] 63
64 def dequeue(self): 65 if self._num == 0: 66 raise QueueUnderflow 67 result = self._elems[self._num-1] 68 self._num -= 1
69 return result 70
71 def enqueue(self,elem): 72 if self.is_full(): 73 self.__extand() 74 for i in range(self._num,0,-1): 75 self._elems[i] = self._elems[i-1] 76 self._elems[0] = elem 77 self._num += 1
78
79 def __extand(self): 80 old_len = self._len 81 self._len *= 2
82 new_elems = [None] * self._len 83 for i in range(old_len): 84 new_elems[i] = self._elems[i] 85 self._elems = new_elems 86
87
88 #循环顺序表实现队列,头部删除和查看O(1),尾部加入O(1)
89 class SQueue(object): 90 def __init__(self, init_num = 8): 91 self._len = init_num 92 self._elems = [None] * init_num 93 self._head = 0 94 self._num = 0 95
96 def is_empty(self): 97 return self._num == 0 98
99 def peek(self): 100 if self.is_empty(): 101 raise QueueUnderflow 102 return self._elems[self._head] 103
104 def dequeue(self): 105 if self.is_empty(): 106 raise QueueUnderflow 107 result = self._elems[self._head] 108 self._head = (self._head + 1) % self._len 109 self._num -= 1
110 return result 111
112 def enqueue(self, elem): 113 if self._num == self._len: 114 self.__extand() 115 self._elems[(self._head + self._num) % self._len] = elem 116 self._num += 1
117
118 def __extand(self): 119 old_len = self._len 120 self._len *= 2
121 new_elems = [None] * self._len 122 for i in range(old_len): 123 new_elems[i] = self._elems[(self._head + i) % old_len] 124 self._elems, self._head = new_elems, 0 125
126
127
128 if __name__=="__main__": 129 q = SQueue() 130 for i in range(8): 131 q.enqueue(i) 132 #for i in range(8):
133 # print(q.dequeue())
134 #print(q._num)
135 q.enqueue(8) 136 print(q._len)