Question

Write your code in the file StringRec.java. For this problem, the following restrictions apply:

YOUR CODE MUST BE RECURSIVE.

Do not use loops (while, do/while, or for).

Do not declare any variables outside of a method. You may declare local variables inside a method.

Complete the following method:

public static String decompress(String compressedText): Decompress the input text, which has been compressed using the RLE algorithm (previous hw assignment):

Run-length encoding (RLE) is a simple "compression algorithm" (an algorithm which takes a block of data and reduces its size, producing a block that contains the same information in less space). It works by replacing repetitive sequences of identical data items with short "tokens" that represent entire sequences. Applying RLE to a string involves finding sequences in the string where the same character repeats. Each such sequence should be replaced by a "token" consisting of:

the number of characters in the sequence

the repeating character

If a character does not repeat, it should be left alone.

For example, consider the following string:

qwwwwwwwwweeeeerrtyyyyyqqqqwEErTTT

After applying the RLE algorithm, this string is converted into:

q9w5e2rt5y4qw2Er3T

In the compressed string, "9w" represents a sequence of 9 consecutive lowercase "w" characters. "5e" represents 5 consecutive lowercase "e" characters, etc.

Answer 1

//importing packages

import java.util.*;

import java.io.*;

//Declaring class name as StringRec

public class StringRec{

//main method start

    public static void main(String[] args) {

//Asking user for enter text compressing text

        System.out.println("What text do you want to decompress?");

//reading input and storing into text variable

        String text = IO.readString();

//calling decompress method for printing o/p

        System.out.println(decompress(text));

    }

// decompress method as static takes text string type argument and returns String variable

    public static String decompress(String text) {

//if input length is less than 1 then return text      

if (text.length()<=1){

            return text;

        }

//declaring local variables

        String firstcharacter="";

        String rest="";

        char c = text.charAt(0);

        if (Character.isLetter(c) == true) {

            firstcharacter = text.substring(0,1);

            rest = text.substring(1);

            return firstcharacter + decompress(rest);

        } else {

            firstcharacter = text.substring(1,2);

            rest = text.substring(2);

            int x = text.charAt(0)-'0';

            char y = text.charAt(1);

            String tst = "";

//declaring local variable in else block

int i = 0;

//calling append method for recursively appending reaming string

append(String tst);

            }//else

return tst + decompress(rest);

        } //decompress()

//append static method takes tst string type argument and returns String variable

public static String append(String tst) {

            if(i >= x) {

             i = 0;

           return tst;

            }

            else return append(tst + y);

         }//append()

}//main

}//class

i/p: qwwwwwwwwweeeeerrtyyyyyqqqqwEErTTT

o/p: q9w5e2rt5y4qw2Er3T