### Java Program to Print Pascal's Triangle - The Coding Shala

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In this post, we will learn how to print Pascal's triangle using the Java program.

## Java Program to Print Pascal's Triangle

Write a Java program to print Pascal's triangle with the given number of rows.

**Example 1:**

Input: 3

Output:

1

1 1

1 2 1

### Solution 1

Before writing the program let's see the properties of Pascal's triangle.

- Every row starts with 1 and ends with 1.
- All the other elements in the triangle follow this rule =>
**(arr[row][column] = arr[row-1][column] + arr[row-1][column-1]).**

We can use 2D ArrayList to generate Pascal's triangle using two for loops. Time Complexity will be O(n^2).

**Java Program: **

import java.util.ArrayList; import java.util.List; import java.util.Scanner; /** * https://www.thecodingshala.com/ */ public class Main { public static List<List<Integer>> generate(int numRows) { List<List<Integer>> res = new ArrayList<>(); for(int i=0; i<numRows; i++) { List<Integer> temp = new ArrayList<>(); for(int j=0; j<=i; j++) { if(j == 0 || j == i) { // first and last element of each row temp.add(1); } else { int val = res.get(i-1).get(j) + res.get(i-1).get(j-1); temp.add(val); } } res.add(temp); } return res; } public static void main(String[] args) { System.out.println("Enter number of rows for Pascal's Triangle"); Scanner sc = new Scanner(System.in); int rows = sc.nextInt(); List<List<Integer>> res = generate(rows); // print the triangle System.out.println("Pascal's Triangle with " + rows + " rows is:"); for (int i = 0; i < rows; i++) { // left spacing for(int j = 0; j < rows-i; j++) { System.out.print(" "); } // print values for(int j = 0; j <= i; j++) { System.out.print(res.get(i).get(j) + " "); } System.out.println(); } } }

**Output: **

Enter number of rows for Pascal's Triangle 5 Pascal's Triangle with 5 rows is: 1 1 1 1 2 1 1 3 3 1 1 4 6 4 1

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