// Tyler Mi
// 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

import java.util.*;
public class Recursion2 {
   public static void main(String[] args) {
      System.out.println("The repeated version of -348 is " + repeat(-348));

      int[] arr = {3, 1, -4, 7, 2};
      System.out.println("The sum of " + Arrays.toString(arr) + " is " + sum(arr));   
   }  
   
   // Returns a version of n, where each digit is repeated
   public static int repeat(int n) {
      if (n < 0) {
         return -1 * repeat(-1 * n);
      } else if (n < 10) {
         return 11 * n;
      } else {
         int lastDigit = n % 10;
         int leadDigits = n / 10;
         return repeat(leadDigits) * 100 + 11 * lastDigit;
      }
   }
   
   // 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) {
         return 0;
      } else {
         return arr[index] + sum(arr, index + 1);
      }
   }
   
//    public static int sum(int[] array) {
//       int sum = 0;
//       for (int i = 0; i < array.length; i++) {
//          sum += array[i];
//       }
//       return sum;
//    }
}