// Erika Wolfe 
// Prints out the sum of an array
import java.util.*;
 
public class Recursion2 {
    public static void main(String[] args) {
        int[] arr = {3, 1, 7, 2};
        System.out.println("The sum of " + Arrays.toString(arr)
                + " is " + sum(arr));
    }
    
    // post: returns the sum of arr
    public static int sum(int[] arr) {
        return sum(arr, 0);
    }
    
    // pre: 0 <= index <= arr.length 
    // post: returns the sum of arr starting at the given index 
    private static int sum(int[] arr, int index) {
        // what is the easiest index to sum in an array?
        if (index == arr.length) {   
            return 0;
        } else {
            return arr[index] + sum(arr, index + 1);
            // this index     + sum of rest of array 
        }
    }
    
//     // iterative solution for the same problem
//     public static int sum2(int[] arr) {
//     //  values that we're using: i, sum, arr
//         int sum = 0; 
//         for (int i = 0; i < arr.length; i++) {
//             sum += arr[i];
//         }
//         return sum;
//     }   
}