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157 lines
3.6 KiB
Python
157 lines
3.6 KiB
Python
"""A Queue using a linked list like structure"""
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from __future__ import annotations
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from collections.abc import Iterator
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from typing import Any
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class Node:
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def __init__(self, data: Any) -> None:
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self.data: Any = data
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self.next: Node | None = None
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def __str__(self) -> str:
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return f"{self.data}"
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class LinkedQueue:
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"""
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>>> queue = LinkedQueue()
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>>> queue.is_empty()
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True
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>>> queue.put(5)
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>>> queue.put(9)
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>>> queue.put('python')
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>>> queue.is_empty()
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False
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>>> queue.get()
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5
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>>> queue.put('algorithms')
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>>> queue.get()
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9
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>>> queue.get()
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'python'
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>>> queue.get()
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'algorithms'
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>>> queue.is_empty()
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True
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>>> queue.get()
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Traceback (most recent call last):
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...
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IndexError: dequeue from empty queue
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"""
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def __init__(self) -> None:
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self.front: Node | None = None
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self.rear: Node | None = None
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def __iter__(self) -> Iterator[Any]:
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node = self.front
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while node:
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yield node.data
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node = node.next
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def __len__(self) -> int:
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"""
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>>> queue = LinkedQueue()
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>>> for i in range(1, 6):
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... queue.put(i)
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>>> len(queue)
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5
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>>> for i in range(1, 6):
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... assert len(queue) == 6 - i
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... _ = queue.get()
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>>> len(queue)
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0
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"""
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return len(tuple(iter(self)))
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def __str__(self) -> str:
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"""
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>>> queue = LinkedQueue()
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>>> for i in range(1, 4):
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... queue.put(i)
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>>> queue.put("Python")
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>>> queue.put(3.14)
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>>> queue.put(True)
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>>> str(queue)
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'1 <- 2 <- 3 <- Python <- 3.14 <- True'
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"""
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return " <- ".join(str(item) for item in self)
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def is_empty(self) -> bool:
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"""
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>>> queue = LinkedQueue()
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>>> queue.is_empty()
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True
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>>> for i in range(1, 6):
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... queue.put(i)
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>>> queue.is_empty()
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False
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"""
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return len(self) == 0
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def put(self, item: Any) -> None:
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"""
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>>> queue = LinkedQueue()
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>>> queue.get()
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Traceback (most recent call last):
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...
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IndexError: dequeue from empty queue
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>>> for i in range(1, 6):
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... queue.put(i)
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>>> str(queue)
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'1 <- 2 <- 3 <- 4 <- 5'
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"""
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node = Node(item)
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if self.is_empty():
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self.front = self.rear = node
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else:
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assert isinstance(self.rear, Node)
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self.rear.next = node
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self.rear = node
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def get(self) -> Any:
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"""
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>>> queue = LinkedQueue()
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>>> queue.get()
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Traceback (most recent call last):
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...
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IndexError: dequeue from empty queue
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>>> queue = LinkedQueue()
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>>> for i in range(1, 6):
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... queue.put(i)
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>>> for i in range(1, 6):
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... assert queue.get() == i
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>>> len(queue)
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0
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"""
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if self.is_empty():
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raise IndexError("dequeue from empty queue")
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assert isinstance(self.front, Node)
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node = self.front
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self.front = self.front.next
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if self.front is None:
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self.rear = None
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return node.data
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def clear(self) -> None:
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"""
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>>> queue = LinkedQueue()
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>>> for i in range(1, 6):
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... queue.put(i)
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>>> queue.clear()
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>>> len(queue)
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0
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>>> str(queue)
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''
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"""
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self.front = self.rear = None
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if __name__ == "__main__":
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from doctest import testmod
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testmod()
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