Merge pull request #1758 from akgmage/dev

add stack using queue

Author: akgmage

Stacks/stack_using_queue.cpp

@@ -0,0 +1,87 @@
+// stack using queue
+#include <iostream>
+#include <queue>
+
+class StackUsingQueues {
+public:
+    StackUsingQueues() {}
+
+    // Push an element onto the stack.
+    void push(int x) {
+        // Add the element to the primary queue.
+        primaryQueue.push(x);
+    }
+
+    // Remove and return the top element of the stack.
+    int pop() {
+        if (isEmpty()) {
+            throw std::runtime_error("Stack is empty");
+        }
+
+        // Move elements from the primary queue to the temporary queue except the last one.
+        while (primaryQueue.size() > 1) {
+            tempQueue.push(primaryQueue.front());
+            primaryQueue.pop();
+        }
+
+        // Get the last element from the primary queue (top of the stack).
+        int topElement = primaryQueue.front();
+        primaryQueue.pop();
+
+        // Swap the primary and temporary queues.
+        primaryQueue = tempQueue;
+        while (!tempQueue.empty()) {
+            tempQueue.pop();
+        }
+
+        return topElement;
+    }
+
+    // Return the top element of the stack without removing it.
+    int top() {
+        if (isEmpty()) {
+            throw std::runtime_error("Stack is empty");
+        }
+
+        int topElement = pop();
+
+        // Add the top element back to the stack.
+        push(topElement);
+
+        return topElement;
+    }
+
+    // Check if the stack is empty.
+    bool isEmpty() {
+        return primaryQueue.empty();
+    }
+
+private:
+    std::queue<int> primaryQueue;
+    std::queue<int> tempQueue;
+};
+
+int main() {
+    StackUsingQueues stack;
+
+    // Push elements onto the stack.
+    stack.push(1);
+    stack.push(2);
+    stack.push(3);
+
+    // Pop elements from the stack.
+    std::cout << stack.pop() << std::endl; // Output: 3
+    std::cout << stack.pop() << std::endl; // Output: 2
+
+    // Push more elements.
+    stack.push(4);
+    stack.push(5);
+
+    // Peek at the top element.
+    std::cout << stack.top() << std::endl; // Output: 5
+
+    // Check if the stack is empty.
+    std::cout << stack.isEmpty() << std::endl; // Output: 0 (false)
+
+    return 0;
+}