Python/data_structures/stacks/stack_using_two_queues.py
K Anamithra b2636d90b3
added implementing stack using two queues ()
* added implementing stack using two queues

* Update Stack using two queues

* Update stack_using_two_queues.py

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* Update stack_using_two_queues.py

* Update stack_using_two_queues.py

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* Update stack_using_two_queues.py

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* Update stack_using_two_queues.py

* Update stack_using_two_queues.py

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Christian Clauss <cclauss@me.com>
2023-10-15 18:41:29 +02:00

86 lines
2.2 KiB
Python

from __future__ import annotations
from collections import deque
from dataclasses import dataclass, field
@dataclass
class StackWithQueues:
"""
https://www.geeksforgeeks.org/implement-stack-using-queue/
>>> stack = StackWithQueues()
>>> stack.push(1)
>>> stack.push(2)
>>> stack.push(3)
>>> stack.peek()
3
>>> stack.pop()
3
>>> stack.peek()
2
>>> stack.pop()
2
>>> stack.pop()
1
>>> stack.peek() is None
True
>>> stack.pop()
Traceback (most recent call last):
...
IndexError: pop from an empty deque
"""
main_queue: deque[int] = field(default_factory=deque)
temp_queue: deque[int] = field(default_factory=deque)
def push(self, item: int) -> None:
self.temp_queue.append(item)
while self.main_queue:
self.temp_queue.append(self.main_queue.popleft())
self.main_queue, self.temp_queue = self.temp_queue, self.main_queue
def pop(self) -> int:
return self.main_queue.popleft()
def peek(self) -> int | None:
return self.main_queue[0] if self.main_queue else None
if __name__ == "__main__":
import doctest
doctest.testmod()
stack: StackWithQueues | None = StackWithQueues()
while stack:
print("\nChoose operation:")
print("1. Push")
print("2. Pop")
print("3. Peek")
print("4. Quit")
choice = input("Enter choice (1/2/3/4): ")
if choice == "1":
element = int(input("Enter an integer to push: ").strip())
stack.push(element)
print(f"{element} pushed onto the stack.")
elif choice == "2":
popped_element = stack.pop()
if popped_element is not None:
print(f"Popped element: {popped_element}")
else:
print("Stack is empty.")
elif choice == "3":
peeked_element = stack.peek()
if peeked_element is not None:
print(f"Top element: {peeked_element}")
else:
print("Stack is empty.")
elif choice == "4":
del stack
stack = None
else:
print("Invalid choice. Please try again.")