Using Java... Instead of diving headfirst into recursion, let us first get our f

Question

Using Java...

Instead of diving headfirst into recursion, let us first get our feet wet. Let us try two different ways to write a function to calculate the sum of the first n integers, and we will call it sumn. sumn(1) = 1 sumn (2) = 1 + 2 = 3 sumn (3) = 1 + 2 + 3 = 6... Write a function of the form, int sumn (int n){...} that calculates the above sum by using a for loop. Now use recursion to write another function which calculates the same quantity by using recursion. Call the function sumn_r Note that sumn_r(1) = 1 sumn_r(2) = 2 + sumn_r(1) sumn_r(3) = 3 + sumn_r(2) and furthermore sumn_r(n) = n + sumn_r (n-1) Use the above relation to define the sumn_r function recursively.

Explanation / Answer

SumOfN.java

import java.util.Scanner;

public class SumOfN {
       int sumn(int n){
           int sum =0;
           for(int i=1; i<=n ; i++){
           sum = sum + i;
           }
           return sum;
           }
           int sumn_r(int n){
           if(n == 0){
           return 0;
           }
           else{
           return n + sumn_r(n-1);
           }
           }
   public static void main(String[] args) {
       Scanner scan = new Scanner(System.in);
       System.out.print("Enter n value: ");
       int n = scan.nextInt();
       SumOfN obj = new SumOfN();
       System.out.println("Sum of "+n+" number using non recursive is "+obj.sumn(n));
       System.out.println("Sum of "+n+" number using recursive is "+obj.sumn_r(n));
   }

}

Output:

Enter n value: 5
Sum of 5 number using non recursive is 15
Sum of 5 number using recursive is 15

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