From b2636d90b3fe697ff64a62b928edfbeccf216e8a Mon Sep 17 00:00:00 2001
From: K Anamithra <anamithrak@gmail.com>
Date: Sun, 15 Oct 2023 22:11:29 +0530
Subject: [PATCH] added implementing stack using two queues (#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>
---
 .../stacks/stack_using_two_queues.py          | 85 +++++++++++++++++++
 1 file changed, 85 insertions(+)
 create mode 100644 data_structures/stacks/stack_using_two_queues.py

diff --git a/data_structures/stacks/stack_using_two_queues.py b/data_structures/stacks/stack_using_two_queues.py
new file mode 100644
index 000000000..4b73246a0
--- /dev/null
+++ b/data_structures/stacks/stack_using_two_queues.py
@@ -0,0 +1,85 @@
+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.")