Introduction

Printing pattern programs is a common programming exercise for understanding loops and conditional logic in C#. A pyramid pattern is a good example because it requires controlling both spaces and asterisks based on the current row.

In this example, we will print a centered pyramid using * characters. The value 7 represents the number of rows.

The expected output is:

      *
     ***
    *****
   *******
  *********
 ***********
*************

C# Pyramid Pattern Program

The following program uses nested for loops to print the pyramid.

using System;

public class Program
{
    public static void Main()
    {
        PrintPyramid(7);
    }

    static void PrintPyramid(int n)
    {
        for (int i = 1; i <= n; i++)
        {
            for (int j = 1; j <= (n * 2 - 1); j++)
            {
                if (j <= n - i || j >= n + i)
                    Console.Write(" ");
                else
                    Console.Write("*");
            }

            Console.WriteLine();
        }
    }
}

How the Logic Works

The method accepts the number of rows through the n parameter:

PrintPyramid(7);

Therefore, the program creates a pyramid with seven rows.

The outer loop controls the rows:

for (int i = 1; i <= n; i++)

For n = 7, the loop executes seven times.

The inner loop controls the positions in each row:

for (int j = 1; j <= (n * 2 - 1); j++)

A pyramid with n rows requires a maximum width of:

2 × n - 1

For seven rows:

2 × 7 - 1 = 13

So every row is evaluated across 13 character positions.

Understanding the Condition

The most important part of the program is:

if (j <= n - i || j >= n + i)
    Console.Write(" ");
else
    Console.Write("*");

The condition determines whether the current position should contain a space or an asterisk.

For the first row:

i = 1
n = 7

The star positions are:

7

For the second row:

i = 2

The star positions are:

6 7 8

For the third row:

i = 3

The star positions are:

5 6 7 8 9

The number of stars increases by two for every new row.

Dry Run

For n = 7, the program produces the following pattern:

Row

Spaces Before

Stars

Total Width

1

6

1

13

2

5

3

13

3

4

5

13

4

3

7

13

5

2

9

13

6

1

11

13

7

0

13

13

The general formula for the number of stars in row i is:

2 × i - 1

The number of leading spaces is:

n - i

This is what keeps the pyramid centered.

Output

Running the program with:

PrintPyramid(7);

produces:

      *
     ***
    *****
   *******
  *********
 ***********
*************

Why Use n * 2 - 1 Positions?

The widest row contains 2n - 1 stars.

For example, with seven rows:

2 × 7 - 1 = 13

The final row therefore contains 13 asterisks:

*************

Using the same width for every row allows the program to position the stars correctly in the center.

Time and Space Complexity

The outer loop runs n times, and the inner loop runs approximately 2n - 1 times for every row.

Therefore, the time complexity is:

O(n²)

The program does not use additional data structures proportional to the input size, so its auxiliary space complexity is:

O(1)

The output itself naturally requires O(n²) characters because the program prints approximately n² positions.

A More Direct Way to Think About the Pattern

The same pyramid can be understood using two simple formulas:

Leading spaces = n - i
Stars          = 2 × i - 1

For n = 7:

Row 1 → 6 spaces + 1 star
Row 2 → 5 spaces + 3 stars
Row 3 → 4 spaces + 5 stars
Row 4 → 3 spaces + 7 stars
Row 5 → 2 spaces + 9 stars
Row 6 → 1 space  + 11 stars
Row 7 → 0 spaces + 13 stars

This approach makes the pattern easier to understand and also provides a foundation for solving other programming-pattern problems.

Conclusion

The pyramid pattern is a simple but useful C# programming exercise for practicing nested loops and conditional statements.

The key idea is to divide every row into character positions and determine whether each position should contain a space or an asterisk. The pyramid contains 2 × i - 1 stars on row i, while the number of leading spaces is n - i.

For n = 7, the result is a centered pyramid with seven rows.

Understanding these formulas makes it easier to solve more advanced pattern-printing problems involving pyramids, diamonds, triangles, and other geometric shapes.