Thread: Integer pyramid 1-15

Hi all.

Am almost there with the problem below.

I need to print an integer pyramid between 1 and 15, but when i get above 10 (11 to 15) i have a spacing problem and not sure how to fix this.

Any and all advice is welcome

import java.util.Scanner;
class Q5
{
public static void main (String [] Args)
	{
	Scanner input = new Scanner(System.in);
 
	System.out.print("Enter the number of lines: ");
	int numberOfLines = input.nextInt();
 
	if ((numberOfLines < 1) || (numberOfLines > 15))
		{
		System.out.println("You must enter a number from 1 to 15");
		System.exit(0);
		}
 
	for (int row = 1; row <= numberOfLines; row++)
		{
		for (int column = 1; column <= numberOfLines - row; column++) 
			{
			System.out.print("  ");
			}
		for (int num = row; num >= 1; num--)
			{
			System.out.print(" " + num);
			}
		for (int num = 2; num <= row; num++)
			{
			System.out.print(" " + num);
			}
 
		System.out.println("");
		}
	input.close();
	}
}

I tend to attack these kind of problems differently - not better, necessarily - by generalizing the steps and using simple math where possible:

- calculate the leading spaces
- print the spaces
- print the characters

Looking at your problems, I came up with this generalization:

// each line begins with 2 spaces * total lines to be printed less
// 2 spaces * the current row being printed

For the above, if 15 lines are to be printed, 28 leading spaces will be printed for line 1, and 0 leading spaces will be printed for line 15. As you've already discovered, it's a bit more complicated than that, so the rest of my generalization is:

// if the total number of lines to be printed is greater than 9,
// an extra space must be added to the single-digit lines for each
// of the double-digit lines

// if the current row being printed is > 9 and < the total number of
// lines, reduce leading spaces by 1 for each row > 9 except the last

// print the leading spaces

// print the required numbers

// add a linefeed