|
| 1 | +from __future__ import annotations |
| 2 | + |
| 3 | +from collections import deque |
| 4 | +from dataclasses import dataclass, field |
| 5 | + |
| 6 | + |
| 7 | +@dataclass |
| 8 | +class StackWithQueues: |
| 9 | + """ |
| 10 | + https://www.geeksforgeeks.org/implement-stack-using-queue/ |
| 11 | +
|
| 12 | + >>> stack = StackWithQueues() |
| 13 | + >>> stack.push(1) |
| 14 | + >>> stack.push(2) |
| 15 | + >>> stack.push(3) |
| 16 | + >>> stack.peek() |
| 17 | + 3 |
| 18 | + >>> stack.pop() |
| 19 | + 3 |
| 20 | + >>> stack.peek() |
| 21 | + 2 |
| 22 | + >>> stack.pop() |
| 23 | + 2 |
| 24 | + >>> stack.pop() |
| 25 | + 1 |
| 26 | + >>> stack.peek() is None |
| 27 | + True |
| 28 | + >>> stack.pop() |
| 29 | + Traceback (most recent call last): |
| 30 | + ... |
| 31 | + IndexError: pop from an empty deque |
| 32 | + """ |
| 33 | + |
| 34 | + main_queue: deque[int] = field(default_factory=deque) |
| 35 | + temp_queue: deque[int] = field(default_factory=deque) |
| 36 | + |
| 37 | + def push(self, item: int) -> None: |
| 38 | + self.temp_queue.append(item) |
| 39 | + while self.main_queue: |
| 40 | + self.temp_queue.append(self.main_queue.popleft()) |
| 41 | + self.main_queue, self.temp_queue = self.temp_queue, self.main_queue |
| 42 | + |
| 43 | + def pop(self) -> int: |
| 44 | + return self.main_queue.popleft() |
| 45 | + |
| 46 | + def peek(self) -> int | None: |
| 47 | + return self.main_queue[0] if self.main_queue else None |
| 48 | + |
| 49 | + |
| 50 | +if __name__ == "__main__": |
| 51 | + import doctest |
| 52 | + |
| 53 | + doctest.testmod() |
| 54 | + |
| 55 | + stack: StackWithQueues | None = StackWithQueues() |
| 56 | + while stack: |
| 57 | + print("\nChoose operation:") |
| 58 | + print("1. Push") |
| 59 | + print("2. Pop") |
| 60 | + print("3. Peek") |
| 61 | + print("4. Quit") |
| 62 | + |
| 63 | + choice = input("Enter choice (1/2/3/4): ") |
| 64 | + |
| 65 | + if choice == "1": |
| 66 | + element = int(input("Enter an integer to push: ").strip()) |
| 67 | + stack.push(element) |
| 68 | + print(f"{element} pushed onto the stack.") |
| 69 | + elif choice == "2": |
| 70 | + popped_element = stack.pop() |
| 71 | + if popped_element is not None: |
| 72 | + print(f"Popped element: {popped_element}") |
| 73 | + else: |
| 74 | + print("Stack is empty.") |
| 75 | + elif choice == "3": |
| 76 | + peeked_element = stack.peek() |
| 77 | + if peeked_element is not None: |
| 78 | + print(f"Top element: {peeked_element}") |
| 79 | + else: |
| 80 | + print("Stack is empty.") |
| 81 | + elif choice == "4": |
| 82 | + del stack |
| 83 | + stack = None |
| 84 | + else: |
| 85 | + print("Invalid choice. Please try again.") |
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