Java Program to Print Star Pascal's Triangle

JavaObject Oriented ProgrammingProgramming

In this article, we will understand how to print star Pascal’s triangle. The Pascal’s triangle is formed by using multiple for-loops and print statements. All values outside the triangle are considered zero (0). The first row is 0 1 0 whereas only 1 acquire a space in Pascal’s triangle, 0s are invisible. The second row is acquired by adding (0+1) and (1+0). The output is sandwiched between two zeroes. The process continues till the required level is achieved.

Below is a demonstration of the same −

Input

Suppose our input is −

Enter the number of rows in Pascal's Triangle : 8

Output

The desired output would be −

Suppose our input is −

Enter the number of rows in Pascal's Triangle : 8
The Pascal's Triangle :
        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

Algorithm

Step 1 - START
Step 2 - Declare three integer values namely i, j and my_input
Step 3 - Read the required values from the user/ define the values
Step 4 - Define a function ‘factorial()’ to compute the factorial of two numbers and a function ‘Combination()’ to compute combination of two numbers
Step 5 - We iterate through two nested 'for' loops to get space between the characters.
Step 6 - After iterating through the innermost loop, we iterate through another 'for' loop. This will help Combination values of ‘i’ and ‘j’.
Step 7 - Now, print a newline to get the specific number of Combination values of ‘i’ and ‘j’ in the subsequent lines.
Step 8 - Display the result
Step 9 - Stop

Example 1

Here, the input is being entered by the user based on a prompt. You can try this example live in our coding ground tool run button.

import java.util.Scanner;
public class PascalsTriangle {
   static int factorial(int my_input) {
      int factors;
      for(factors = 1; my_input > 1; my_input--){
         factors *= my_input;
      }
      return factors;
   }
   static int combination(int my_input,int r) {
      return factorial(my_input) / ( factorial(my_input-r) * factorial(r) );
   }
   public static void main(String args[]){
      System.out.println();
      int my_input, i, j;
      my_input = 5;
      System.out.println("Required packages have been imported");
      Scanner my_scanner = new Scanner(System.in);
      System.out.println("A reader object has been defined ");
      System.out.print("Enter the number of rows in Pascal's Triangle : ");
      my_input = my_scanner.nextInt();
      System.out.println("The Pascal's Triangle : ");
      for(i = 0; i <= my_input; i++) {
         for(j = 0; j <= my_input-i; j++){
            System.out.print(" ");
         }
        for(j = 0; j <= i; j++){
           System.out.print(" "+combination(i, j));
        }
        System.out.println();
     }
   }
}

Output

Required packages have been imported
A reader object has been defined
Enter the number of rows in Pascal's Triangle : 8
The Pascal's Triangle :
         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

Example 2

Here, the integer has been previously defined, and its value is accessed and displayed on the console.

public class PascalsTriangle {
   static int factorial(int my_input) {
      int factors;
      for(factors = 1; my_input > 1; my_input--){
         factors *= my_input;
      }
      return factors;
   }
   static int combination(int my_input,int r) {
      return factorial(my_input) / ( factorial(my_input-r) * factorial(r) );
   }
   public static void main(String args[]){
      System.out.println();
      int my_input, i, j;
      my_input = 8;
      System.out.println("The number of rows in Pascal's Triangle is defined as " +my_input);
      System.out.println("The Pascal's Triangle : ");
      for(i = 0; i <= my_input; i++) {
         for(j = 0; j <= my_input-i; j++){
            System.out.print(" ");
         }
         for(j = 0; j <= i; j++){
            System.out.print(" "+combination(i, j));
         }
         System.out.println();
      }
   }
}

Output

The number of rows in Pascal's Triangle is defined as 8
The Pascal's Triangle :
        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
raja
Updated on 25-Feb-2022 11:58:52

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