Help -My Pascal Triangle program breaks down at row 13- I've spent hours!

[abraxas91]

Hi, my name is Stephan. I've been working on this program off and on over the past few days. I have yet to perfect it. I would really appreciate any help! For some reason the output begins to deteriorate at around row 13...I can't figure out why.
Thank you in advance,
Stephan

import java.io.*;
import java.util.*;
import gpdraw.*;
import java.lang.*;
public class pascal{
int[] array= new int[1000];
public void generate(int input){
    int i=0;
    for(int n=0;n<=input;n++){
       for(int r=0 ; r<=n;r++){
           array[i] = fact(n)/(fact(n-r)*fact(r));
           i++;
    }}
    int d=0;
    for (int row = 0; row <=input; row++){
        for(int pos=0; pos<=row; pos++){
            System.out.print(" " + array[d]);
            d++;
} 
System.out.println();
 
}}
public static int fact(int x){
        if( x <= 1 )     // base case
            return 1;
        else
            return x * fact( x - 1 );
    }
}

DRIVER

import java.util.Scanner;
public class pascaldriver{
public static void main(String[] args){
    int input;
    Scanner nub= new Scanner(System.in);
    System.out.print("Enter the row you want the pascal triangle to go to: ");
    input = nub.nextInt();
 
pascal tri = new pascal();
    tri.generate(input);}

OUTPUT

Enter the row you want the pascal triangle to go to: 13
 1
 1 1
 1 2 1
 1 3 3 1
 1 4 6 4 1
 1 5 10 10 5 1
 1 6 15 20 15 6 1
 1 7 21 35 35 21 7 1
 1 8 28 56 70 56 28 8 1
 1 9 36 84 126 126 84 36 9 1
 1 10 45 120 210 252 210 120 45 10 1
 1 11 55 165 330 462 462 330 165 55 11 1
 1 12 66 220 495 792 924 792 495 220 66 12 1
 1 4 24 88 221 399 532 532 399 221 88 24 4 1

Starts at row 0 as well as position 0 on each row.

The more rows I enter the more senseless the output becomes.

1
 1 1
 1 2 1
 1 3 3 1
 1 4 6 4 1
 1 5 10 10 5 1
 1 6 15 20 15 6 1
 1 7 21 35 35 21 7 1
 1 8 28 56 70 56 28 8 1
 1 9 36 84 126 126 84 36 9 1
 1 10 45 120 210 252 210 120 45 10 1
 1 11 55 165 330 462 462 330 165 55 11 1
 1 12 66 220 495 792 924 792 495 220 66 12 1
 1 4 24 88 221 399 532 532 399 221 88 24 4 1
 1 0 1 5 14 29 44 50 44 29 14 5 1 0 1
 1 1 -4 -1 2 4 7 9 9 7 4 2 -1 -4 1 1
 1 0 -1 -1 -1 4 -1 1 1 1 -1 4 -1 -1 -1 0 1
 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1

I wouldn't post unless I had spent a few hours on this...
I WOULD REALLY APPRECIATE ANY HELP AT ALL!

[Ganon11]

It probably has to do with the factorial being used. 13! is likely too big to hold in an int. This isn't your fault, so don't blame your code or yourself - that's just how Java was made.

If you have a desperate need to go to 13 rows and beyond, you need to look into alternate data types to use.

[Laharl]

Yep, 13! is 6,227,020,800, which is too big for the 4billion or so a 32bit integer (which is all Java has) can handle. Use a long instead, that's 64 bits and will thus get you to 2^63-1, which is 9.22*10^18.

[JosAH]

I'd say don't use factorials at all. A number at line i, column j is the sum of the
two numbers diagonally above it, i.e (i-1, j-1) and (i-1, j). If you calculate those
numbers from right to left you can use the same array over and over again.
Here's a spoiler so no comments nor an explanation:

public class Pascal {
 
    public static void main(String[] args) {
 
        int[] n= new int[20];
 
        for (int i= 0; i < n.length; i++) {
            n[i]= 1;
            for (int j= i; --j > 0; n[j]+= n[j-1]);
            for(int j= 0; j <= i; j++)
                System.out.print(n[j]+" ");
            System.out.println();
        }
    }
}

kind regards,

Jos