stack_by_two_queues.py

from collections import deque
from typing import Generic, TypeVar

T = TypeVar("T")
""" Implementing stack using two arrays"""


class Stack(Generic[T]):  # Stack class to implement stack operations
    def __init__(self):
        self.insert_queue = deque()  # First Queue to be used for inserting
        self.second_queue = deque()  # Second Queue to be used

    def push(self, item: int):
        self.insert_queue.append(item)
        while self.second_queue:
            self.insert_queue.append(
                self.second_queue.popleft()
            )  # Popping the elements

        self.insert_queue, self.second_queue = self.second_queue, self.insert_queue

    def pop(self) -> int:
        if not self.second_queue:  # if the stack  is empty
            return None
        return self.second_queue.popleft()  # if not empty pop

    def top(self) -> int:
        if not self.second_queue:
            return None
        return self.second_queue[0]

    def __str__(self) -> str:
        return tuple(self.second_queue)

    def __len__(self) -> int:
        return len(self.second_queue)


def test_stack() -> None:
    stack = Stack()  # Creating a empty stack
    choice = int(
        input("1 to push,2 to pop,3 to peek ,4 to print, 5 for size,6 to exit:")
    )
    while choice in (1, 2, 3, 4, 5, 6):
        match (choice):
            case 1:
                element = int(input("Enter the element to push:"))
                stack.push(element)
            case 2:
                print(stack.pop())
            case 3:
                print(stack.top())
            case 4:
                print(stack.__str__())
            case 5:
                leng = stack.__len__()
                print(f"The size of the stack is {leng}")
            case 6:
                print("Exiting")
                break
            case _:
                print("Enter properly")

        choice = int(
            input("1 to push,2 to pop,3 to peek ,4 to print, 5 for size,6 to exit:")
        )


if __name__ == "__main__":
    test_stack()  # calling the test function