// Hunter Schafer, CSE 143
// Program prints out the sum of an array
import java.util.Arrays;

public class RecursionExamples {
    public static void main(String[] args) {
        int[] arr = {3, 1, 7, 2};
        System.out.println("The sum of " + Arrays.toString(arr)
                + " is " + sum(arr));
    }
    
    // pre: arr is not null
    // returns the sum of all the elements in the given arr
    public static int sum(int[] arr) {
        return sum(arr, 0);
    }
    
    // pre: arr is not null, 0 <= index <= arr.length
    // returns the sum of the elements of arr starting at 
    // the given index to the end.
    private static int sum(int[] arr, int index) {  
        if (index == arr.length) {
            return 0;
        } else {
            // arr[0] + arr[1] + arr[2] + ... 
            // sum one number with the rest of the numbers
            // arr[0] + sum(of arr starting at 1)
            //          arr[1] + sum(of arr starting at 2)
            //                   arr[2] + sum(of arr starting at 3)
            return arr[index] + sum(arr, index + 1);
        }
        
    }
    
    /*
     * int sum = 0;
     * for (int  i= 0; i < arr.lenght; i++) {
     *     sum += arr[i];
     * }
     * return sum;
     * 
     * 
     */
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
}