Question

recursively take two strings that are NOT THE SAME and return the string that consists of all the letters that appear in both string1 and string2 using only string1 and string2 as inputs with NO LOOPS. This must be done recursively.

for example, if string1 is "fourth" and string2 is "faster" the string returned is "frt"

LANGUAGE IS JAVA

Answer 1

Program

class Assignment
{
   //method to return a String contains all the characters
   //that consists of both the String inputs
   public static String stringsConsists(String s1, String s2)
   {
       //base condition
       if(s1.length()==0 || s2.length()==0)
           return "";
       //extract first character
       char c = s1.charAt(0);
       //check if c is found in the String s2
       if(s2.contains(""+c))
           return ("" + c + stringsConsists(s1.substring(1), s2));
       //if c is found in the String s2
       return (stringsConsists(s1.substring(1), s2));
   }
  
   //main method
   public static void main (String[] args)
   {
       String s1 = "fourth";
       String s2 = "faster";
      
       String s3 = stringsConsists(s1, s2);
      
       System.out.println(s3);
   }
}

Output:

frt

N.B. Whether you face any problem then share with me in the comment section, I'll happy to help you.