隊列 / Queue

數組隊列

數組隊列是隊列基於數組的一種實現，其實現類似於數組棧，是一種FIFO的線性數據結構。

Queue:
        <--| 1 | 2 | 3 | 4 | 5 |<--

下面將使用Python中的list來替代C語言中的數組實現數組隊列的數據結構。

Note: 這裏的實現並沒有像C語言中的申請一塊固定大小的數組，手動的定制數組中隊列的頭尾位置，而是利用list的特性直接完成，因此較為簡單。

數組隊列的實現與數組棧的實現基本類似，同時入列和出列也十分簡單，僅需要對數組進行操作即可。

這裏直接給出完整代碼和運行結果，實現過程可參考數組棧的實現。

後續再補充固定數組大小的隊列實現。

完整代碼

  1 class QueueEmptyException(Exception): pass
  2 
  3 
  4 class QueueFullException(Exception): pass
  5 
  6 
  7 class Queue:
  8     """
  9     Queue:
 10         <--| 1 | 2 | 3 | 4 | 5 |<--
 11     """
 12     def __init__(self, max=0):
 13         self.queue = []
 
 14         self._max = max
 15         self.max = max
 16 
 17     def __str__(self):
 18         return ‘ | ‘.join(map(str, self.queue))
 19 
 20     def init(self, iterable=()):
 21         if not iterable:
 22             return 
 23         self.queue.extend(list(iterable))
 24 
 25     @property
 
 26     def max(self):
 27         return self._max
 28 
 29     @max.setter
 30     def max(self, m):
 31         m = int(m)
 32         if m < self.length:
 33             raise Exception(‘Resize queue failed, please dequeue some elements first.‘)
 34         self._max = m
 35         if self._max < 0:
 36             self._max = 0
 37 
 38     def show(self):
 39         print(self)
 40 
 41     @property
 42     def length(self):
 43         return len(self.queue)
 44 
 45     @property
 46     def is_empty(self):
 47         return not bool(self.queue)
 48 
 49     @property
 50     def is_full(self):
 51         return bool(self._max and self.length == self._max)
 52 
 53     def enqueue(self, item):
 54         if self.is_full:
 55             raise QueueFullException(‘Error: trying to enqueue element into a full queue‘)
 56         self.queue.append(item)
 57     
 58     def dequeue(self):
 59         if self.is_empty:
 60             raise QueueEmptyException(‘Error: trying to dequeue element from an empty queue‘)
 61         front = self.queue[0]
 62         self.queue = self.queue[1:]
 63         return front
 64 
 65     def clear(self):
 66         self.queue = []
 67 
 68 
 69 def test(queue):
 70     print(‘\nInit queue:‘)
 71     queue.init([1, 2, 3, 4, 5, 6, 7])
 72     queue.show()
 73 
 74     print(‘\nEnqueue element to queue:‘)
 75     queue.enqueue(‘like‘)
 76     queue.show()
 77 
 78     print(‘\nDequeue element from queue:‘)
 79     e = queue.dequeue()
 80     print(‘Element %s deququed,‘ % e)
 81     queue.show()
 82 
 83     print(‘\nSet queue max size:‘)
 84     try:
 85         queue.max = 1
 86     except Exception as e:
 87         print(e)
 88 
 89     print(‘\nSet queue max size:‘)
 90     queue.max = 7
 91     print(queue.max)
 92 
 93     print(‘\nEnqueue full queue:‘)
 94     try:
 95         queue.enqueue(7)
 96     except QueueFullException as e:
 97         print(e)
 98 
 99     print(‘\nClear queue:‘)
100     queue.clear()
101     queue.show()
102 
103     print(‘\nQueue is empty:‘)
104     print(queue.is_empty)
105 
106     print(‘\nDequeue empty queue:‘)
107     try:
108         queue.dequeue()
109     except QueueEmptyException as e:
110         print(e)
111 
112 if __name__ == ‘__main__‘:
113     test(Queue())

運行得到結果

Init queue:
1 | 2 | 3 | 4 | 5 | 6 | 7

Enqueue element to queue:
1 | 2 | 3 | 4 | 5 | 6 | 7 | like

Dequeue element from queue:
Element 1 deququed,
2 | 3 | 4 | 5 | 6 | 7 | like

Set queue max size:
Resize queue failed, please dequeue some elements first.

Set queue max size:
7

Enqueue full queue:
Error: trying to enqueue element into a full queue

Clear queue:


Queue is empty:
True

Dequeue empty queue:
Error: trying to dequeue element from an empty queue

相關閱讀

1 數組棧

Python與數據結構[2] -> 隊列/Queue[0] -> 數組隊列的 Python 實現