Question

Thumbs up for help.create a stack and write a program that reverses the letters in a string. Then display. use the LinkedList class in java to implement a stack.

Answer 1

import java.util.*;

class Stack1

{

    LinkedList<Character> l;

    // constructor

    Stack1()

    {

        // create a linked list

        this.l = new LinkedList<Character>();

    }

   

    // return the size of the Stack1

    public int size()

    {

        return l.size();

    }

   

    // push element into Stack1

    public void push(char ch)

    {

        // addFirst() function adds the element in the front of the list

        this.l.addFirst(ch);

    }

   

    // pop element from Stack1

    public char pop()

    {

        // if Stack1 is empty

        if( this.isEmpty() == true )

        {

            System.out.println("Stack1 is empty");

            return ' ';

        }

       

        // get first element in the list

        char ans = this.l.get(0);

       

        // removeFirst() function removes the element from the front of the list

        this.l.removeFirst();

       

        return ans;

    }

   

    public boolean isEmpty()

    {

        return this.size() == 0;

    }

}

class Solution

{

    // return the reversed string of str

    public static String reverse(String str)

    {

        // create a Stack1 to store character

        Stack1 st = new Stack1();

       

        int i;

       

        // traverse the string

        for( i = 0 ; i < str.length() ; i++ )

        {

            // add the character at index i to Stack1

            // charAt(i) return the character at index i in String

            st.push( str.charAt(i) );

        }

       

        // store the reversed String

        String ans = "";

       

        // loop untill Stack1 is empty

        while( !st.isEmpty() )

            // pop the top most element from Stack1 using pop()

            ans += st.pop();

           

        return ans;

    }

   

    public static void main(String[] args)

    {

        // create a Scanner class object

        Scanner sc = new Scanner(System.in);

       

        System.out.print("Enter a sentence : ");

       

        // read complete line

        String str = sc.nextLine();

       

        // split the string using space as delimeter

        String[] arr = str.split(" ");

       

        int i;

       

        // create an array to store reversed words

        String[] rev = new String[ arr.length ];

       

        for( i = 0 ; i < arr.length ; i++ )

            // reverse the current word

            rev[i] = reverse( arr[i] );

           

        System.out.print("\nReversed sentence : ");

           

        for( i = 0 ; i < rev.length ; i++ )

            System.out.print(rev[i] + " ");

    }

}

Sample Output