// Practice.java -- Let's write some recursive functions.  Practically
// anything you can do with a loop, you can also do recursively.
import java.io.*;
import java.util.*;

public class Practice
{
  private static int [] a = { 7, 2, 9, 4, 1, 6 };

  public static void main(String [] args) throws IOException
  {
    // simple I/O examples
    System.out.println("List of numbers:  " + count(10));
    System.out.println("The sum 1..10 equals " + sum(10));  
    System.out.println("Star pattern:\n" + triangle(5));

    // practice with strings
    BufferedReader kbd = new BufferedReader(new InputStreamReader(System.in));
    System.out.print("\nEnter a string:  ");
    String s = kbd.readLine();
    System.out.println("Reversal is:  " + reverse(s));
    System.out.println("palindrome() returns " + palindrome(s));

    // practice with a string tokenizer
    System.out.print("Enter a list of numbers:  ");
    s = kbd.readLine();
    StringTokenizer tok = new StringTokenizer(s, ", ");
    System.out.println("\nsum is " + sumToken(tok));

    // practice with arrays
    System.out.println("The largest element of the array is " + max(a, 0));
    System.out.println("Array sum is " + sumArray(a, 0));
  }

  public static String count(int n)
  {




  }


  public static int sum(int n)
  {





  }

  // Print a row (horizontal line) of stars.
  public static String starLine(int n)
  {





  }

  // Make a right triangle filled with stars.  Makes use of starLine()
  // above to simulate a nested loop.
  // In the recursive case, we make sure to print the first n-1 rows, then
  // append the current row of stars, and then a newline.
  public static String triangle(int n)
  {






  }

  public static String reverse(String s)
  {





  }

  public static boolean palindrome(String s)
  {







  }

  // Recursion can also replace a "while" loop.
  // Here we find the sum of numbers that are tokens in a string.
  public static int sumToken(StringTokenizer tok)
  {





  }

  // Find the largest element of (at least part of) an array.
  // We take 3 parameters - the array and the starting index.
  public static int max(int [] a, int start)
  {










  }

  // Find the sum of the elements in an array.  Analogous to finding the max.
  public static int sumArray(int [] a, int start)
  {






  }
}