Question

Recursive Tracing. For each call to the following method, indicate what value is returned:

public static int mystery(int n) {

if (n < 0) {

return -mystery(-n);

} else if (n == 0) {

return 0;

} else {

return mystery(n / 10) * 10 + 9 - (n % 10);

}

Call Value Returned mystery(0) mystery(5) mystery(13) mystery(297) mystery(-3456)

}

Can any one help me with it?

Answer 1

Dear Student ,

As per the requirement submitted above , kindly find the below solution.

Here a new java program with name "main.java" is created, which contains following code.

main.java :

//Main class
public class Main
{ //Main method
   public static void main(String[] args) {
   //call to method
       System.out.println("mystery(5) : "+mystery(5));
   }
   //method defination
   public static int mystery(int n)
   { //if n is less than 0
if (n < 0)
{
return -mystery(-n);
}
//if n=0
else if (n==0)
{
return 0; //return 0
}
else
{ //return recursive call
return mystery(n / 10) * 10 + 9 - (n % 10);
}
   }
}

======================================================

Output : Compile and Run above program , will get the screen as shown below

Screen 1 :Screen when mystery(0) called

Screen 2 :Screen when mystery(5) called

Screen 3 :Screen when mystery(13) called

Screen 4 :Screen when mystery(297) called

Screen 5 :Screen when mystery(-3456) called

Below table shows details

Call	Value Returned
mystery(0)	0
mystery(5)	4
mystery(13)	86
mystery(297)	702
mystery(-3456)

NOTE : PLEASE FEEL FREE TO PROVIDE FEEDBACK ABOUT THE SOLUTION.