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Commit b2636d9

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anamithrak15pre-commit-ci[bot]cclauss
authored
added implementing stack using two queues (TheAlgorithms#10076)
* added implementing stack using two queues * Update Stack using two queues * Update stack_using_two_queues.py * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci * Update stack_using_two_queues.py * Update stack_using_two_queues.py * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci * Update stack_using_two_queues.py * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci * 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>
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from __future__ import annotations
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from collections import deque
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from dataclasses import dataclass, field
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@dataclass
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class StackWithQueues:
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"""
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https://www.geeksforgeeks.org/implement-stack-using-queue/
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>>> stack = StackWithQueues()
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>>> stack.push(1)
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>>> stack.push(2)
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>>> stack.push(3)
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>>> stack.peek()
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3
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>>> stack.pop()
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3
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>>> stack.peek()
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2
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>>> stack.pop()
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2
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>>> stack.pop()
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1
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>>> stack.peek() is None
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True
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>>> stack.pop()
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Traceback (most recent call last):
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...
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IndexError: pop from an empty deque
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"""
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main_queue: deque[int] = field(default_factory=deque)
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temp_queue: deque[int] = field(default_factory=deque)
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def push(self, item: int) -> None:
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self.temp_queue.append(item)
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while self.main_queue:
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self.temp_queue.append(self.main_queue.popleft())
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self.main_queue, self.temp_queue = self.temp_queue, self.main_queue
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def pop(self) -> int:
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return self.main_queue.popleft()
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def peek(self) -> int | None:
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return self.main_queue[0] if self.main_queue else None
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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stack: StackWithQueues | None = StackWithQueues()
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while stack:
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print("\nChoose operation:")
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print("1. Push")
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print("2. Pop")
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print("3. Peek")
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print("4. Quit")
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choice = input("Enter choice (1/2/3/4): ")
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if choice == "1":
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element = int(input("Enter an integer to push: ").strip())
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stack.push(element)
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print(f"{element} pushed onto the stack.")
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elif choice == "2":
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popped_element = stack.pop()
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if popped_element is not None:
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print(f"Popped element: {popped_element}")
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else:
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print("Stack is empty.")
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elif choice == "3":
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peeked_element = stack.peek()
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if peeked_element is not None:
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print(f"Top element: {peeked_element}")
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else:
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print("Stack is empty.")
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elif choice == "4":
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del stack
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stack = None
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else:
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print("Invalid choice. Please try again.")

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