Pascal triangle in java using array

Let’s learn pascal triangle in java using array.

Pascal triangle in java using array

Here’s the algorithm to write pascal triangle using arrays we have to use two dimensional array. First declare integer variables num, a, b, arr[][], p.

Let user input value of variable ‘num’. Now set p = num – 1. In the next step set two dimensional array arr = new int[num][num].

Now using two for loops repeat for a = 0 to num (a < num) and for b = 0 to a(b <= a). In the next step using if else check if b == 0 or b == 1 then set arr[a][b] = 1, else set arr[a][b] = arr[a – 1][b – 1] + arr[a – 1][b]; display output.

Now repeat for loop for a = 0 to num (a < num), for b = 0 to p and leave blank space. Decrease value of variable p by 1.

Repeat for loop for b = 0 to a (b <= a). print blank space. Here’s program to display pascal triangle using array.

import java.util.Scanner;
public class PascalTriangleUsingArray
{
   public static void main(String[] args)
   {
      Scanner sc = new Scanner(System.in);
      int num, a, b, arr[][], p;
      System.out.println("Please enter number of rows: ");
      num = sc.nextInt();
      p = num - 1;
      arr = new int[num][num];
      for(a = 0; a < num; a++)
      {
         for(b = 0; b <= a; b++)
            if(b == 0 || b == a)
               arr[a][b] = 1;
            else
               arr[a][b] = arr[a - 1][b - 1] + arr[a - 1][b];
      }
      System.out.println("Pascal's triangle: \n");
      for(a = 0; a < num; a++)
      {
         for(b = 0; b <= p; b++)
            System.out.print(" ");
         p--;
         for(b = 0; b <= a; b++)
            System.out.print(arr[a][b] + " ");
         System.out.println();
      }
      sc.close();
   }
}

Output:

Please enter number of rows:
6
Pascal’s triangle:
1
1 1
1 2 1
1 3 3 1
1 4 6 4 1
1 5 10 10 5 1