C#: Swap the top two elements of a stack

C# Sharp Stack: Exercise-15 with Solution

Write a C# program to swap the top two elements of a given stack.

Sample Solution:

C# Code:

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

public class Stack
{
    private int[] items; // Array to hold stack elements
    private int top; // Index indicating the top of the stack

    // Constructor to initialize the stack with a specified size
    public Stack(int size)
    {
        items = new int[size]; // Creating an array of integers with the given size
        top = -1; // Initializing top index to -1 indicating an empty stack
    }

    // Check if the stack is empty
    public bool IsEmpty()
    {
        return top == -1; // Stack is empty if top is -1
    }

    // Check if the stack is full
    public bool IsFull()
    {
        return top == items.Length - 1; // Stack is full if top equals the last index of the array
    }

    // Push an element onto the stack
    public void Push(int item)
    {
        if (IsFull()) // Check if the stack is full
        {
            Console.WriteLine("Stack Full!"); // Display a message indicating stack overflow
            return;
        }

        items[++top] = item; // Increment top and add the item to the stack
    }

    // Pop an element from the stack
    public int Pop()
    {
        if (IsEmpty()) // Check if the stack is empty
        {
            Console.WriteLine("Stack underflow"); // Display a message indicating stack underflow
            return -1;
        }

        return items[top--]; // Return and decrement top to remove the element from the stack
    }

    // Peek at the top element of the stack without removing it
    public int Peek()
    {
        if (IsEmpty()) // Check if the stack is empty
        {
            Console.WriteLine("Stack is empty"); // Display a message indicating the stack is empty
            return -1;
        }

        return items[top]; // Return the top element of the stack
    }

    // Static method to get the size of a stack
    public static int Size(Stack stack)
    {
        return stack.top + 1; // Return the size of the stack based on the current top index
    }

    // Static method to count all the elements in a stack
    public static int Count(Stack stack)
    {
        int count = 0; // Initialize count variable to track the number of elements

        Stack temp = new Stack(Size(stack)); // Create a temporary stack to preserve the original stack order

        // Move elements from the original stack to the temporary stack and count them
        while (!stack.IsEmpty())
        {
            temp.Push(stack.Pop()); // Move elements from original stack to temporary stack
            count++; // Increment count for each element moved
        }

        // Restore the original stack by moving elements back from the temporary stack
        while (!temp.IsEmpty())
        {
            stack.Push(temp.Pop()); // Move elements back to the original stack
        }

        return count; // Return the total count of elements in the stack
    }

    // Static method to clear the stack by popping all elements
    public static void Clear(Stack stack)
    {
        while (!stack.IsEmpty())
        {
            stack.Pop(); // Remove elements from the stack until it's empty
        }
    }

    // Method to swap the top two elements of a stack
    public static void SwapTopTwo(Stack stack)
    {
        if (Count(stack) < 2) // Check if there are at least two elements in the stack
        {
            return; // If there are not enough elements, exit without performing the swap
        }

        int top = stack.Pop(); // Pop the top element of the stack
        int secondTop = stack.Pop(); // Pop the second top element of the stack
        stack.Push(top); // Push the previously top element to the stack in the second top position
        stack.Push(secondTop); // Push the previously second top element to the stack in the top position
    }

    // Method to display the elements of the stack
    public static void Display(Stack stack)
    {
        if (stack.IsEmpty()) // Check if the stack is empty
        {
            Console.WriteLine("Stack is empty"); // Display a message indicating the stack is empty
            return;
        }

        Console.WriteLine("Stack elements:"); // Display a message indicating stack elements will be shown
        for (int i = stack.top; i >= 0; i--) // Loop through the stack elements
        {
            Console.Write(stack.items[i] + " "); // Print each element of the stack
        }
    }

}

public class Program
{
    public static void Main(string[] args)
    {
        Console.WriteLine("Initialize a stack:");
        Stack stack = new Stack(10); // Create a stack with a capacity of 10 elements
        Console.WriteLine("Input some elements onto the stack:");
        stack.Push(1); // Add elements to the stack
        stack.Push(2);
        stack.Push(3);
        stack.Push(4);
        stack.Push(5);
        stack.Push(6);
        Stack.Display(stack); // Display the initial stack elements
        Console.WriteLine("\n\nSwap the top two elements of a stack:");
        Stack.SwapTopTwo(stack); // Swap the top two elements of the stack
        Stack.Display(stack); // Display the stack after the swap
    }
}

Sample Output:

Initialize a stack:
Input some elements onto the stack:
Stack elements:
6 5 4 3 2 1

Swap the top two elements of a stack:
Stack elements:
5 6 4 3 2 1

Flowchart:

C# Sharp Code Editor:

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