// HW08_2e.java
// Tim Hilby
// Created on April 12, 2006
import java.util.Scanner;

public class HW08_2e
{
   // calculates the nth row of Pascal's Triangle
   // returns null if n is not positive
   public static int[] row(int n)
   {
      int[] prevRow;
      int[] curRow;
      if (n <= 0)
      {
         // invalid row number
         curRow = null;
      }
      else if (n == 1)
      {
         // trivial base case
         curRow = new int[1];
         curRow[0] = 1;
      }
      else
      {
         // first get the previous row
         prevRow = row(n - 1);
         // now build the current row
         curRow = new int[n];
         // the ends are both 1
         curRow[0] = 1;
         curRow[n - 1] = 1;
         // now build the middle
         for (int i = 1; i < (n - 1); i++)
         {
            curRow[i] = prevRow[i - 1] + prevRow[i];
         }
      }
      return curRow;
   }

   public static void main(String[] args)
   {
      Scanner scan = new Scanner(System.in);
      
      System.out.print("This program prints the Nth");
      System.out.println("line of Pascal's Triangle.");
      System.out.println("What is N? (type 0 to quit)");
      int n = scan.nextInt();
      while (n != 0)
      {
         if (n < 0)
         {
            System.out.println("N must be a positive number!");
         }
         else
         {
            System.out.print("Answer:");
            int[] nthrow = row(n);
            for (int i = 0; i < n; i++)
            {
               System.out.print(" " + nthrow[i]);
            }
            System.out.println();
         }
         System.out.println("What is N? (type 0 to quit)");
         n = scan.nextInt();
      }
   }
}