mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-10-06 21:59:30 +00:00
5cb0a000c4
* Queue implementation using two Stacks * fix typo in queue/queue_on_two_stacks.py * add 'iterable' to queue_on_two_stacks initializer * make queue_on_two_stacks.py generic class * fix ruff-UP007 in queue_on_two_stacks.py * enhance readability in queue_on_two_stacks.py * Create queue_by_two_stacks.py --------- Co-authored-by: Christian Clauss <cclauss@me.com>
116 lines
2.6 KiB
Python
116 lines
2.6 KiB
Python
"""Queue implementation using two stacks"""
|
|
|
|
from collections.abc import Iterable
|
|
from typing import Generic, TypeVar
|
|
|
|
_T = TypeVar("_T")
|
|
|
|
|
|
class QueueByTwoStacks(Generic[_T]):
|
|
def __init__(self, iterable: Iterable[_T] | None = None) -> None:
|
|
"""
|
|
>>> QueueByTwoStacks()
|
|
Queue(())
|
|
>>> QueueByTwoStacks([10, 20, 30])
|
|
Queue((10, 20, 30))
|
|
>>> QueueByTwoStacks((i**2 for i in range(1, 4)))
|
|
Queue((1, 4, 9))
|
|
"""
|
|
self._stack1: list[_T] = list(iterable or [])
|
|
self._stack2: list[_T] = []
|
|
|
|
def __len__(self) -> int:
|
|
"""
|
|
>>> len(QueueByTwoStacks())
|
|
0
|
|
>>> from string import ascii_lowercase
|
|
>>> len(QueueByTwoStacks(ascii_lowercase))
|
|
26
|
|
>>> queue = QueueByTwoStacks()
|
|
>>> for i in range(1, 11):
|
|
... queue.put(i)
|
|
...
|
|
>>> len(queue)
|
|
10
|
|
>>> for i in range(2):
|
|
... queue.get()
|
|
1
|
|
2
|
|
>>> len(queue)
|
|
8
|
|
"""
|
|
|
|
return len(self._stack1) + len(self._stack2)
|
|
|
|
def __repr__(self) -> str:
|
|
"""
|
|
>>> queue = QueueByTwoStacks()
|
|
>>> queue
|
|
Queue(())
|
|
>>> str(queue)
|
|
'Queue(())'
|
|
>>> queue.put(10)
|
|
>>> queue
|
|
Queue((10,))
|
|
>>> queue.put(20)
|
|
>>> queue.put(30)
|
|
>>> queue
|
|
Queue((10, 20, 30))
|
|
"""
|
|
return f"Queue({tuple(self._stack2[::-1] + self._stack1)})"
|
|
|
|
def put(self, item: _T) -> None:
|
|
"""
|
|
Put `item` into the Queue
|
|
|
|
>>> queue = QueueByTwoStacks()
|
|
>>> queue.put(10)
|
|
>>> queue.put(20)
|
|
>>> len(queue)
|
|
2
|
|
>>> queue
|
|
Queue((10, 20))
|
|
"""
|
|
|
|
self._stack1.append(item)
|
|
|
|
def get(self) -> _T:
|
|
"""
|
|
Get `item` from the Queue
|
|
|
|
>>> queue = QueueByTwoStacks((10, 20, 30))
|
|
>>> queue.get()
|
|
10
|
|
>>> queue.put(40)
|
|
>>> queue.get()
|
|
20
|
|
>>> queue.get()
|
|
30
|
|
>>> len(queue)
|
|
1
|
|
>>> queue.get()
|
|
40
|
|
>>> queue.get()
|
|
Traceback (most recent call last):
|
|
...
|
|
IndexError: Queue is empty
|
|
"""
|
|
|
|
# To reduce number of attribute look-ups in `while` loop.
|
|
stack1_pop = self._stack1.pop
|
|
stack2_append = self._stack2.append
|
|
|
|
if not self._stack2:
|
|
while self._stack1:
|
|
stack2_append(stack1_pop())
|
|
|
|
if not self._stack2:
|
|
raise IndexError("Queue is empty")
|
|
return self._stack2.pop()
|
|
|
|
|
|
if __name__ == "__main__":
|
|
from doctest import testmod
|
|
|
|
testmod()
|