Merge pull request #1756 from akgmage/dev

add stack using queue

Author: akgmage

Stacks/stack_using_queue.go

@@ -0,0 +1,84 @@
+// stack using queue
+package main
+
+import (
+	"container/list"
+	"fmt"
+)
+
+// Stack represents a stack data structure using two queues.
+type Stack struct {
+	queue1 *list.List // Primary queue
+	queue2 *list.List // Temporary queue for operations
+}
+
+// Constructor creates a new stack.
+func NewStack() *Stack {
+	return &Stack{
+		queue1: list.New(),
+		queue2: list.New(),
+	}
+}
+
+// Push adds an element to the top of the stack.
+func (s *Stack) Push(value int) {
+	// Add the element to the primary queue
+	s.queue1.PushBack(value)
+}
+
+// Pop removes and returns the top element of the stack.
+func (s *Stack) Pop() int {
+	// Move elements from the primary queue to the temporary queue except the last one
+	for s.queue1.Len() > 1 {
+		element := s.queue1.Front()
+		s.queue1.Remove(element)
+		s.queue2.PushBack(element.Value)
+	}
+
+	// Get the last element from the primary queue (top of the stack)
+	topElement := s.queue1.Front().Value
+
+	// Swap the primary and temporary queues
+	s.queue1, s.queue2 = s.queue2, s.queue1
+
+	return topElement.(int)
+}
+
+// Top returns the top element of the stack without removing it.
+func (s *Stack) Top() int {
+	// Similar to Pop, but don't remove the last element
+	topElement := s.Pop()
+
+	// Add the top element back to the stack
+	s.Push(topElement)
+
+	return topElement
+}
+
+// IsEmpty checks if the stack is empty.
+func (s *Stack) IsEmpty() bool {
+	return s.queue1.Len() == 0
+}
+
+func main() {
+	stack := NewStack()
+
+	// Push elements onto the stack
+	stack.Push(1)
+	stack.Push(2)
+	stack.Push(3)
+
+	// Pop elements from the stack
+	fmt.Println(stack.Pop()) // Output: 3
+	fmt.Println(stack.Pop()) // Output: 2
+
+	// Push more elements
+	stack.Push(4)
+	stack.Push(5)
+
+	// Peek at the top element
+	fmt.Println(stack.Top()) // Output: 5
+
+	// Check if the stack is empty
+	fmt.Println(stack.IsEmpty()) // Output: false
+}