Why does each row have 2*i-1 characters?

Because the inner loop runs while j < i*2, which prints 1, 3, 5, 7, 9 characters for i=1..5.

How does the program alternate numbers and *?

It checks j % 2. Even j prints '*', odd j prints the current row number i.

What is the time complexity?

O(n^2) for n rows because the total printed characters grow quadratically.

Number-Star Diamond Pattern in C#

Q: How does the program alternate numbers and *?

It checks j % 2. Even j prints '*', odd j prints the current row number i.

Q: What is the time complexity?

O(n^2) for n rows because the total printed characters grow quadratically.

Beginner

⏱️ 7 min read

📚 Updated: Aug 2025

🎯 2 Code Examples

Modulo Operator

Number-star diamond output (1 to 5*5*5*5*5 and back to 1) in C# programming

What You’ll Learn

How to print a diamond-like pattern that alternates between the row number and * characters:

1, 2*2, 3*3*3, ... then back down to 1.

⭐ Pattern Output

For n = 5, the pattern looks like this:

Output

1
2*2
3*3*3
4*4*4*4
5*5*5*5*5
4*4*4*4
3*3*3
2*2
1

Complete C# Program

This is the exact reference approach: print the top half with i = 1..5, then print the bottom half with i = 4..1. Use j % 2 to alternate.

using System;

namespace MyApp
{
    class Program
    {
        static void Main(string[] args)
        {
            int i, j;

            for (i = 1; i <= 5; i++)
            {
                for (j = 1; j < i * 2; j++)
                {
                    if (j % 2 == 0)
                        Console.Write("*");
                    else
                        Console.Write(i);
                }
                Console.WriteLine();
            }

            for (i = 4; i >= 1; i--)
            {
                for (j = 1; j < i * 2; j++)
                {
                    if (j % 2 == 0)
                        Console.Write("*");
                    else
                        Console.Write(i);
                }
                Console.WriteLine();
            }
        }
    }
}

Variation — User Input n

Make the height configurable:

using System;

namespace MyApp
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.Write("Enter n: ");
            int n = Convert.ToInt32(Console.ReadLine());
            if (n < 1) return;

            for (int i = 1; i <= n; i++)
            {
                for (int j = 1; j < i * 2; j++)
                    Console.Write((j % 2 == 0) ? "*" : i.ToString());
                Console.WriteLine();
            }

            for (int i = n - 1; i >= 1; i--)
            {
                for (int j = 1; j < i * 2; j++)
                    Console.Write((j % 2 == 0) ? "*" : i.ToString());
                Console.WriteLine();
            }
        }
    }
}