Question

Write the reverseO function recursively. This function takes a string and the length of the string as arguments and returns the same string with its characters in the reverse order

Answer 1

See the other answer for the solution in Java. However, to make the reversing truly recursive, replace it by this:

public static String reverseO(String st,int n)

{

String ret = st.substring(n-1,n);

if (n > 1)

ret += reverseO(st, n-1);

return ret;

}

Step-by-step explanation:

A recursive function calls itself. The function places the last character at the start and then calls itself to do the same on the remainder of the string. Make sure there always is a stop criterium, to end the recursion.

Recursive functions are often elegant, but most of the times not very efficient in terms of stack usage.

Answer 2

// here is code in java.

// import package

import java.util.*;

// class definition

class Main

{

// method that return reverse string

public static String reverseO(String st,int n)

{

// create an empty string

String rev_st="";

for(int x=n-1;x>=0;x--)

{

// append character from last into the empty string

rev_st=rev_st+st.charAt(x);

}

// return the reversed string

return rev_st;

}

// main method of the class

public static void main (String[] args) throws java.lang.Exception

{

try{

// scanner object to read string

Scanner scr=new Scanner(System.in);

System.out.print("enter the string:");

// read the string from user

String st=scr.nextLine();

// find the length of string

int len=st.length();

// call the method with parameter string and length

System.out.println("reverse string is: "+reverseO(st,len));

}catch(Exception ex){

return;}

}

}

Step-by-step explanation:

Read a string from user and assign it to variable "st" and Find its length. Then call the method reverseO() with parameter string and length.Then in the method reverseO(), create an empty string.Then append the characters of input string to empty string from last index.Then return the string.This will be the string in reverse order.

Output:

enter the string:hello

reverse string is: olleh