f36eb15b84
1. 去掉下面的错误代码
<<<<<<< HEAD
self._data[i] = self._items[i + self._head]
=======
2. 按照课程中的java代码，增加“队列为空时，返回None”
43 lines
1.1 KiB
Python
43 lines
1.1 KiB
Python
"""
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Queue based upon array
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用数组实现的队列
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Author: Wenru
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"""
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from typing import Optional
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class ArrayQueue:
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def __init__(self, capacity: int):
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self._items = []
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self._capacity = capacity
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self._head = 0
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self._tail = 0
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def enqueue(self, item: str) -> bool:
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if self._tail == self._capacity:
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if self._head == 0:
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return False
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else:
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for i in range(0, self._tail - self._head):
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self._items[i] = self._items[i + self._head]
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self._tail = self._tail - self._head
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self._head = 0
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self._items.insert(self._tail, item)
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self._tail += 1
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return True
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def dequeue(self) -> Optional[str]:
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if self._head != self._tail:
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item = self._items[self._head]
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self._head += 1
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return item
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else:
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return None
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def __repr__(self) -> str:
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return " ".join(item for item in self._items[self._head : self._tail])
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