Merge pull request #1755 from akgmage/dev

add queue using stack in python

Author: akgmage

Stacks/queue using stack.py

@@ -0,0 +1,38 @@
+# Queue using stack
+class Queue:
+    def __init__(self):
+        self.enqueue_stack = []  # Stack for enqueue operations
+        self.dequeue_stack = []  # Stack for dequeue operations
+
+    def enqueue(self, value):
+        """Enqueue: Add an element to the back of the queue."""
+        self.enqueue_stack.append(value)
+
+    def dequeue(self):
+        """Dequeue: Remove and return the front element of the queue."""
+        # If the dequeue stack is empty, transfer elements from the enqueue stack
+        if not self.dequeue_stack:
+            while self.enqueue_stack:
+                # Pop an element from the enqueue stack and push it onto the dequeue stack
+                element = self.enqueue_stack.pop()
+                self.dequeue_stack.append(element)
+
+        # If the dequeue stack is still empty, the queue is empty
+        if not self.dequeue_stack:
+            raise IndexError("Queue is empty")
+
+        # Pop and return the front element from the dequeue stack
+        return self.dequeue_stack.pop()
+
+# Example usage
+queue = Queue()
+queue.enqueue(1)
+queue.enqueue(2)
+queue.enqueue(3)
+print(queue.dequeue())  # Output: 1
+print(queue.dequeue())  # Output: 2
+queue.enqueue(4)
+queue.enqueue(5)
+print(queue.dequeue())  # Output: 3
+print(queue.dequeue())  # Output: 4
+print(queue.dequeue())  # Output: 5