Question

Use the Summation recursive program you did in the class to also work with minus integers.

For example, the sum of -3 will be -6 which is (-3)+(-2)+(-1)+0. USE THIS CODE

package project5;

import java.util.Scanner;

public class SingleRecursion {
/** Main method */
public static long sum(int n) {
   if (n<0) throw
   new IllegalArgumentException ("Can't calculate factorial of negative");
   if (n==1)
       return 1;
   else if (n==0)
       return 1;
   else
       return n+sum(n-1);
   //return (n<2) ? 1 : n*factorial (n-1);
}
public static void main (String[] args) {
   Scanner stdIn = new Scanner (System.in);
   System.out.print("Factorial of what number do you want to calculate ? ");
   int num = stdIn.nextInt();
   System.out.print( sum (num));
  
   stdIn.close();
  
  
}
  
}
  
  
  
  

Answer 1

package project5;

import java.util.Scanner;

public class SingleRecursion {
    /** Main method */
    public static long sum(int n) {
        if (n==0)
            return 0;
        else if (n<0)
            return n + sum(n+1);
        else
            return n+sum(n-1);
        //return (n<2) ? 1 : n*factorial (n-1);
    }
    public static void main (String[] args) {
        Scanner stdIn = new Scanner (System.in);
        System.out.print("Factorial of what number do you want to calculate ? ");
        int num = stdIn.nextInt();
        System.out.print( sum (num));
        stdIn.close();
    }
}