Thread: Recursion ouput is not coming for value more than 40.

Hello All,

I have written following code using recursion.It is working however it is not giving me ouput for value 50.Infact nothing is display when I enter number greater than 40.

import java.util.Scanner;
 
public class Test {
 
 
	public static void main(String[] args) {
 
		Scanner in =new Scanner(System.in);
		System.out.println("Enter number");
		int n = in.nextInt();
 
		System.out.println(Mymethod(n));
 
	}
 
 
 
public static long Mymethod(long n){
 
	if(n==0){
 
		return 0;
	}
 
	else if(n==1){
 
		return 1;
	}
 
   else if(n==2){
 
		return 1;
	}
	else{
 
	return (Mymethod(n-1))+ (Mymethod(n-2))+ (Mymethod(n-3));
 
	}
}
}

Have you waited long enough for the program to finish?

Hi..Thank you for reply but I waited for around 20 min.

Your algorithm must be doing a lot of recursive calling.
Where did you get the code? Did it give an expression or description of the number of calls it makes.

I have written this code.NO there is no description.Expression was

f(n) =f(n-1)+f(n-2)+f(n-3)

Base case was f(0)=1,f(1)=2,f(2)=1

Question was to write code in java or any object oriented language to return nth number from given expression.

Have you tried an iterative approach vs a recursive one?

Your code doesn't follow the equations:

f(1)=2

else if(n==1){

return 1;

Is there anything wrong in this code?

oh sorry no,it is f(1) =1 only.
sorry for that typing mistake.

I have not yet tried iterative way.

My computer is very slow.Is it running at your end for value 50?

@ copeg:Thanks for reply.I registered today here so sorry about that.

Yes.. I waited around 20 min..Can I write this code using recursion better way?efficient?

there is no exception coming..