Solved

java pascal triangle array program wont compile

Posted on 2009-07-12
6
486 Views
Last Modified: 2013-11-23
hi everyone,

this program is supposed to take a number 'rowCount' as input from a user, then use that number to create an equal number of rows in a pascal triangle. the code initializes pascal0[] and pascal1[] in the PascalTri class to remember values in the current (1) and previous (0) rows.
it's also supposed to print these rows to the console, but i must be doing something wrong because it hasnt worked. can anyone point me in the right direction?

1
11
121
1331
14641
...
public class PascalTri{
 
        public int rowCount;
        int[] pascal1 = new int[0];
        int[] pascal0 = {};
 
        public PascalTri(int row){
            row = rowCount;
            for(int i=0; i<row; i++){
                pascal1[0] = 1;
                pascal1[pascal0.length] = 1;
                pascal1 = new int[pascal0.length+1];
                for(int j=1; j<pascal0.length;j++){
                    pascal1[j] = pascal0[j] + pascal0[j-1];
                }
                pascal0 = pascal1;
                }
            }
       
        public void displayRows(){
            System.out.println(pascal1);
        }
    }
 
=============================================================================
 
import java.util.Scanner;
 
    public class PascalDriver{
      public static void main(String[] args){
        Scanner scan = new Scanner(System.in);
        System.out.println("Enter number of rows");
        int rowCount = scan.nextInt();
        PascalTri t = new PascalTri(rowCount);
        t.displayRows();
      }
    }

Open in new window

0
Comment
Question by:bpiche
  • 3
  • 2
6 Comments
 
LVL 92

Expert Comment

by:objects
ID: 24836631
you need to use a loop in displayRows to display the triangle
0
 

Author Comment

by:bpiche
ID: 24836649
how could I do that short of embedding the displayRows function within the PascalTri function?

thanks again
0
 
LVL 92

Expert Comment

by:objects
ID: 24836703
you need to use a 2d array, following shows how to use it with your current code

import java.util.Scanner;

public class PascalTri {

      int[][] pascal1 = null;

      public PascalTri(int row) {
            
            // create empty triangle
            
            pascal1 = new int[row][];
            
            // initialise first row
            
            pascal1[0] = new int[1];
            pascal1[0][0] = 1;
            
            // calculate remaining rows
            
            for (int i = 1; i < row; i++) {
                  pascal1[i] = new int[i+1];
                  pascal1[i][0] = 1;
                  pascal1[i][i] = 1;
                  for (int j = 1; j < pascal1[i].length; j++) {
                        int[] pascal0 = pascal1[i-1];
                        //pascal1[j] = ...;
                  }
            }
      }

      public void displayRows() {
            for (int i=0; i
0
Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 

Author Comment

by:bpiche
ID: 24836768
is there any way i can do this without 2d arrays? sorry i forgot to mention that >.<
0
 
LVL 92

Accepted Solution

by:
objects earned 125 total points
ID: 24836774
you'd need to print it out as you calculate instead of printing it out from a separate method
0
 
LVL 20

Assisted Solution

by:a_b
a_b earned 125 total points
ID: 24837116
What  I would suggest is that you move the logic from the constructor of the PascalTri class to the displayRows(). Within displayRows(), run loops as shown below -

for(i=0;i<rowCount;i++)
{
     for(j=0;j<i;j++)
         //Print the values 1 upto rowCount
     for(j=i;j>0;--+)
         //Print the values from  rowCount down to 1
}

This is in a nutshell, you might have to fine tune the indexes just a bit.
0

Featured Post

Free Tool: Path Explorer

An intuitive utility to help find the CSS path to UI elements on a webpage. These paths are used frequently in a variety of front-end development and QA automation tasks.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
iterator/ListIterator approach 17 51
maven module vs maven project 3 72
Chrome and Firefox Java 5 67
jsp CRUD operations with and without prepared statement also hibernatge 1 27
By the end of 1980s, object oriented programming using languages like C++, Simula69 and ObjectPascal gained momentum. It looked like programmers finally found the perfect language. C++ successfully combined the object oriented principles of Simula w…
In this post we will learn how to connect and configure Android Device (Smartphone etc.) with Android Studio. After that we will run a simple Hello World Program.
Viewers learn about the third conditional statement “else if” and use it in an example program. Then additional information about conditional statements is provided, covering the topic thoroughly. Viewers learn about the third conditional statement …
Video by: Michael
Viewers learn about how to reduce the potential repetitiveness of coding in main by developing methods to perform specific tasks for their program. Additionally, objects are introduced for the purpose of learning how to call methods in Java. Define …

713 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question