//Pascal's Triangle




import java.io.*;

/**
* This program uses several loops and recursion to create
* a pyramid of factorial numbers. The size of the pyramid 
* is based on a user suplied number
*/

public class PascalTriangle {

	/**
	* The constructor - gets the number of rows from method
	* getNumberOfRows() and then passes it to drawTriangle()
	*/
public PascalTriangle () throws IOException {
	int rows = 0;
	rows = getNumRows();
	drawTriangle(rows);
	}
	
	/**
        * Reads the number in as a String and
        * passes it to a method where it is turned into
        * a long.
        * Then it passes the row number to draw triangle
        * Since java does not have simplifed input and output
        * We must create out own method to read in
        * information, the InputStreamReader and BufferedReader
	*/

public int getNumRows() throws IOException{
       InputStreamReader isr = new InputStreamReader(System.in);
       BufferedReader bis = new BufferedReader(isr);
       String number = "";
       String name; 
       System.out.println("Pascal's Triangle, by Garth Bruen");
       System.out.println();
       System.out.print("Please enter your name: ");
       name = bis.readLine();
       System.out.print("Please enter a row number between 1 and 21: ");
		
	number = bis.readLine();
        System.out.println();
        System.out.println(name + " ,you have requested " + number + " rows.");
        System.out.println();
        System.out.println("Here's " +name+ "'s  triangle!!!");
        System.out.println();
        return (convert(number));
	}
	
	/**
	* Takes a String and returns an int - hence the
	* "throws NumberFormatException" in the method header.
	* CODE TO BE IMPLEMENTED.
	*/
public int convert(String num) throws NumberFormatException{
        int convertedNum = 0;
        convertedNum = Integer.parseInt(num);
        if(convertedNum > 21){
          System.out.println();
          System.out.print("The number is too large and will ");
          System.out.println("not print properly");
          System.out.println("Please run again and re-read instructions");
          System.out.println();
          convertedNum = 0;
          return convertedNum;
                //My invention, an error message which
                //does not print the huge triangle and ends the program
        }
        return convertedNum;
}
        
	/**
	* Returns the factorial of a given number using recursion
	* CODE TO BE IMPLEMENTED
	*/
public long getFactorial(long fact) {       
	long factorialResult = 1;
	if(fact == 0 || fact == 1) {
                return factorialResult;}
        else {
                factorialResult = fact*getFactorial(--fact);
                return factorialResult;
                }
              }

		
	/**
	* Returns the number that goes into each slot of
	* Pascal's triangle.
	* @param r the number of the row
	* @param n the nth element of that row.
        */

public long getPascalNum(int n, int r) {
	long pascalNum = 0;
	pascalNum = (getFactorial(n)/(getFactorial(r)*(getFactorial(n-r))));
	return pascalNum;
	}

	/**
	* The triangle gets drawn in this method. 
	* @param rows how many rows to pass in
        */

public void drawTriangle(int rows) {
	for(int i = 0; i < rows; i++) {
        	for(int j = (rows - i); j > 0; j--){
                System.out.print(" ");
                }
                for(int h = 0; h <= i; h++){
                System.out.print(getPascalNum(i, h) + " ");
                }
         System.out.println();
         }
}

	
public static void main (String args[]) throws IOException {
	
PascalTriangle pt = new PascalTriangle();
	
	}

}