import java.util.*;

// Jeremy Lipschutz
// Program working through some more recursion methods, introducing the idea
// of a public-private pair. The private helper method has parameters that can
// keep track of more information. The public method just needs to start off the
// recursion

public class Recursion2 {
   public static void main(String[] args) {
      
      int[] arr = {5, 2, -15, 10, 2, 7, 9};
      System.out.println("The sum of " + Arrays.toString(arr) + " is " + sum(arr));
      
   }
   
   // Returns the sum of the contents of the array
   public static int sum(int[] arr) {
      return sum(arr, 0);
   }
   
   // Returns the sum of the contents of the array,
   // starting from the given index
   private static int sum(int[] arr, int index) {
      if(index == arr.length) { // finished processing array
         // base case
         return 0;
      } else {
         // recursive cases
         // do a little of the work
         int value = arr[index];
         // recurring on a smaller problem
         return value + sum(arr, index + 1);
      }
   }   
   
   /*
   public static int sum(int[] arr) {
      int sum = 0;
      for(int index = 0; index < arr.length; index++) {
         sum += arr[index];
      }
      return sum;
   } 
   */ 
   
}