import java.util.Scanner;
import java.util.StringTokenizer;

/** Formula4.java -- (this version has diagnostic output)
 */
public class Formula4
{
  private static int invocations = 0;

  public static void main(String [] args)
  {
    System.out.print("Enter two positive integers:  ");
    Scanner kbd = new Scanner(System.in);
    String line = kbd.nextLine();
    StringTokenizer tok = new StringTokenizer(line, ", ");
    int a = Integer.parseInt(tok.nextToken());
    int b = Integer.parseInt(tok.nextToken());
    System.out.printf("You entered %d and %d\n", a, b);

    int expValue = exp(a, b);
    System.out.printf("%d to the %d is %d\n", a, b, expValue);

    int pascalValue = pascal(a, b);
    System.out.printf("pascal() invoked %d times.\n", invocations);
    System.out.printf("Number in row %d col %d of Pascal's triangle = %d\n",
		      a, b, pascalValue);
  }

  public static int exp(int a, int b)
  {
    System.out.printf("exp(%d, %d):  start\n", a, b);
    if (b == 0)
    {
      System.out.printf("exp(%d, %d):  base case, returning 1\n", a, b);
      return 1;
    }
    else if (b % 2 == 0)
    {
      System.out.printf("exp(%d, %d):  Even case, making recursive call" +
			" to exp(%d, %d)\n", a, b, a, b/2);
      int returnValue = exp(a, b/2);

      System.out.printf("exp(%d, %d):  After recursive call, squaring %d " +
			"to return %d\n", a, b, returnValue, 
			returnValue * returnValue);

      return returnValue * returnValue;
    }
    else
    {
      System.out.printf("exp(%d, %d):  Odd case, making recursive call to " +
			"exp(%d, %d)\n", a, b, a, b-1);
      int returnValue = exp(a, b-1);

      System.out.printf("exp(%d, %d):  After recursive call, multiplying " +
			"base %d by %d to return %d\n", a, b, a,
			returnValue, a*returnValue);
      return a * returnValue;
    }
  }

  public static int pascal(int a, int b)
  {
    ++invocations;
    System.out.printf("pascal(%d, %d):  start\n", a, b);
    if (a == b || b == 0)
    {
      System.out.printf("pascal(%d, %d):  base case, returning 1\n", a, b);
      return 1;
    }
    else if (b > a)
    {
      System.out.printf("pascal(%d, %d):  base case, returning 0 - " +
			"we are outside triangle\n", a, b);
      return 0;
    }
    else
    {
      System.out.printf("pascal(%d, %d):  Making left recursive call to " +
			"pascal(%d, %d)\n", a, b, a, b-1);
      int leftValue = pascal(a-1, b-1);
      System.out.printf("pascal(%d, %d):  Left recursive call came back " +
			"with %d\n", a, b, leftValue);

      System.out.printf("pascal(%d, %d):  Making right recursive call to " +
			"pascal(%d, %d)\n", a, b, a-1, b);
      int rightValue = pascal(a-1,b);
      System.out.printf("pascal(%d, %d):  Right recursive call came back " +
			"with %d\n", a, b, rightValue);

      System.out.printf("pascal(%d, %d):  After recursive calls, returning " +
			"%d\n", a, b, leftValue + rightValue);
      return leftValue + rightValue;
    }
  }

}