C#: Find common elements between two stacks

Last update on December 20 2024 12:43:48 (UTC/GMT +8 hours)

Write a C# program that implements a stack and finds common elements between two stacks.

Sample Solution:

C# Code:

using System;
using System.Collections.Generic;

public class Stack
{
    private int[] items; // Array to store stack elements
    private int top; // Index pointing to 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; // Returns true if the stack is empty
    }

    // Check if the stack is full
    public bool IsFull()
    {
        return top == items.Length - 1; // Returns true if the stack is full
    }

    // 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
    }

    // Method to count all the elements in a stack
    public static int Count(Stack stack)
    {
        int count = 0;
        Stack temp = new Stack(Size(stack));

        // Move elements from the original stack to a 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
    }

    // Method to check if an element is present or not in a stack
    public bool Contains(int item)
    {
        for (int i = 0; i <= top; i++)
        {
            if (items[i] == item)
            {
                return true; // Return true if the element is found in the stack
            }
        }

        return false; // Return false if the element is not found in the stack
    }

    // Find common elements between two stacks
    public static Stack FindCommonElements(Stack stack1, Stack stack2)
    {
        Stack commonElements = new Stack(Math.Min(Size(stack1), Size(stack2)));

        // Iterate through stack1 and check for common elements with stack2
        for (int i = 0; i <= stack1.top; i++)
        {
            int item = stack1.items[i];
            // Check if the element exists in stack2 and is not already present in commonElements
            if (stack2.Contains(item) && !commonElements.Contains(item))
            {
                commonElements.Push(item); // Add the common element to the commonElements stack
            }
        }

        return commonElements; // Return the stack containing common elements
    }

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

        Console.WriteLine("Stack elements:");
        for (int i = stack.top; i >= 0; i--)
        {
            Console.Write(stack.items[i] + " ");
        }
    }
}

public class Program
{
    public static void Main(string[] args)
    {
        Console.WriteLine("Initialize three stacks:");
        // Create and display the first stack
        Stack stack1 = new Stack(10);
        stack1.Push(1);
        stack1.Push(2);
        stack1.Push(3);
        Console.Write("Stack1: ");
        Stack.Display(stack1);

        // Create and display the second stack
        Stack stack2 = new Stack(10);
        stack2.Push(2);
        stack2.Push(3);
        stack2.Push(4);
        stack2.Push(5);
        Console.Write("\nStack2: ");
        Stack.Display(stack2);

        // Create and display the third stack
        Stack stack3 = new Stack(10);
        stack3.Push(3);
        stack3.Push(4);
        stack3.Push(5);
        Console.Write("\nStack3: ");
        Stack.Display(stack3);

        // Find and display common elements between Stack1 and Stack2
        Stack commonStack1and2 = Stack.FindCommonElements(stack1, stack2);
        Console.Write("\n\nCommon elements between Stack1 and Stack2: ");
        Stack.Display(commonStack1and2);

        // Find and display common elements between Stack1 and Stack3
        Stack commonStack1and3 = Stack.FindCommonElements(stack1, stack3);
        Console.Write("\n\nCommon elements between Stack1 and Stack3: ");
        Stack.Display(commonStack1and3);

        // Find and display common elements between Stack2 and Stack3
        Stack commonStack2and3 = Stack.FindCommonElements(stack2, stack3);
        Console.Write("\n\nCommon elements between Stack2 and Stack3: ");
        Stack.Display(commonStack2and3);
    }
}

Sample Output:

Initialize three stacks:
Stack1: Stack elements:
3 2 1 
Stack2: Stack elements:
5 4 3 2 
Stack3: Stack elements:
5 4 3 

Common elements between Stack1 and Stack2: Stack elements:
3 2 

Common elements between Stack1 and Stack3: Stack elements:
3 

Common elements between Stack2 and Stack3: Stack elements:
5 4 3

Flowchart:

C# Sharp Code Editor:

Improve this sample solution and post your code through Disqus

Previous: Checks if two stacks are equal.
Next: Stack elements in the first but not in the second.