Python/data_structures/queues/linked_queue.py at master · twilight-debugger/Python · GitHub

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"""A Queue using a linked list like structure"""

from __future__ importannotations

fromcollections.abcimportIterator
fromtypingimportAny


classNode:
def__init__(self, data: Any) ->None:
self.data: Any=data
self.next: Node|None=None

def__str__(self) ->str:
returnf"{self.data}"


classLinkedQueue:
"""
 >>> queue = LinkedQueue()
 >>> queue.is_empty()
 True
 >>> queue.put(5)
 >>> queue.put(9)
 >>> queue.put('python')
 >>> queue.is_empty()
 False
 >>> queue.get()
 5
 >>> queue.put('algorithms')
 >>> queue.get()
 9
 >>> queue.get()
 'python'
 >>> queue.get()
 'algorithms'
 >>> queue.is_empty()
 True
 >>> queue.get()
 Traceback (most recent call last):
 ...
 IndexError: dequeue from empty queue
 """

def__init__(self) ->None:
self.front: Node|None=None
self.rear: Node|None=None

def__iter__(self) ->Iterator[Any]:
node=self.front
whilenode:
yieldnode.data
node=node.next

def__len__(self) ->int:
"""
 >>> queue = LinkedQueue()
 >>> for i in range(1, 6):
 ... queue.put(i)
 >>> len(queue)
 5
 >>> for i in range(1, 6):
 ... assert len(queue) == 6 - i
 ... _ = queue.get()
 >>> len(queue)
 0
 """
returnlen(tuple(iter(self)))

def__str__(self) ->str:
"""
 >>> queue = LinkedQueue()
 >>> for i in range(1, 4):
 ... queue.put(i)
 >>> queue.put("Python")
 >>> queue.put(3.14)
 >>> queue.put(True)
 >>> str(queue)
 '1 <- 2 <- 3 <- Python <- 3.14 <- True'
 """
return" <- ".join(str(item) foriteminself)

defis_empty(self) ->bool:
"""
 >>> queue = LinkedQueue()
 >>> queue.is_empty()
 True
 >>> for i in range(1, 6):
 ... queue.put(i)
 >>> queue.is_empty()
 False
 """
returnlen(self) ==0

defput(self, item: Any) ->None:
"""
 >>> queue = LinkedQueue()
 >>> queue.get()
 Traceback (most recent call last):
 ...
 IndexError: dequeue from empty queue
 >>> for i in range(1, 6):
 ... queue.put(i)
 >>> str(queue)
 '1 <- 2 <- 3 <- 4 <- 5'
 """
node=Node(item)
ifself.is_empty():
self.front=self.rear=node
else:
assertisinstance(self.rear, Node)
self.rear.next=node
self.rear=node

defget(self) ->Any:
"""
 >>> queue = LinkedQueue()
 >>> queue.get()
 Traceback (most recent call last):
 ...
 IndexError: dequeue from empty queue
 >>> queue = LinkedQueue()
 >>> for i in range(1, 6):
 ... queue.put(i)
 >>> for i in range(1, 6):
 ... assert queue.get() == i
 >>> len(queue)
 0
 """
ifself.is_empty():
raiseIndexError("dequeue from empty queue")
assertisinstance(self.front, Node)
node=self.front
self.front=self.front.next
ifself.frontisNone:
self.rear=None
returnnode.data

defclear(self) ->None:
"""
 >>> queue = LinkedQueue()
 >>> for i in range(1, 6):
 ... queue.put(i)
 >>> queue.clear()
 >>> len(queue)
 0
 >>> str(queue)
 ''
 """
self.front=self.rear=None


if__name__=="__main__":
fromdoctestimporttestmod

testmod()