C# Program to Print Star Pattern

You can print a star pattern in C# using nested for loops; for example, for (int i = 1; i <= 5; i++) { for (int j = 1; j <= i; j++) { Console.Write("*"); } Console.WriteLine(); } prints a right-angled triangle of stars.

Examples

Input5

Output* ** *** **** *****

Input3

Output* ** ***

Input1

Output*

How to Think About It

To print a star pattern, think of rows and columns. For each row, print stars equal to the row number. Use one loop to go through rows and a nested loop to print stars in each row.

Algorithm

1

Get the number of rows to print.

2

Start a loop from 1 to the number of rows.

3

Inside this loop, start another loop from 1 to the current row number.

4

Print a star in the inner loop without moving to a new line.

5

After the inner loop ends, move to the next line.

6

Repeat until all rows are printed.

Code

csharp

using System;
class Program {
    static void Main() {
        int rows = 5;
        for (int i = 1; i <= rows; i++) {
            for (int j = 1; j <= i; j++) {
                Console.Write("*");
            }
            Console.WriteLine();
        }
    }
}

Output

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

Dry Run

Let's trace the program with rows = 3 to see how stars print.

1

Start outer loop with i=1

Inner loop runs j=1 to 1, prints '*' once, then moves to new line.

2

Outer loop i=2

Inner loop runs j=1 to 2, prints '**', then moves to new line.

3

Outer loop i=3

Inner loop runs j=1 to 3, prints '***', then moves to new line.

i (row)	j (star count)	Output line
1	1	*
2	2	**
3	3	***

Why This Works

Step 1: Outer loop controls rows

The outer for loop runs from 1 to the number of rows, deciding how many lines to print.

Step 2: Inner loop prints stars

The inner for loop runs from 1 to the current row number, printing stars on the same line.

Step 3: Move to next line

After printing stars for a row, Console.WriteLine() moves the cursor to the next line for the next row.

Alternative Approaches

Using while loops

csharp

using System;
class Program {
    static void Main() {
        int rows = 5;
        int i = 1;
        while (i <= rows) {
            int j = 1;
            while (j <= i) {
                Console.Write("*");
                j++;
            }
            Console.WriteLine();
            i++;
        }
    }
}

This uses while loops instead of for loops; it works the same but is less concise.

Using string constructor

csharp

using System;
class Program {
    static void Main() {
        int rows = 5;
        for (int i = 1; i <= rows; i++) {
            Console.WriteLine(new string('*', i));
        }
    }
}

This uses <code>new string('*', i)</code> to create star strings directly, making code shorter and clearer.

Complexity: O(n^2) time, O(1) space

Time Complexity

The program uses nested loops where the outer loop runs n times and the inner loop runs up to n times, resulting in O(n^2) time.

Space Complexity

The program uses a fixed amount of extra space regardless of input size, so space complexity is O(1).

Which Approach is Fastest?

Using new string('*', i) is faster and cleaner than nested loops because it avoids manual printing inside loops.

Approach	Time	Space	Best For
Nested for loops	O(n^2)	O(1)	Learning loops and control flow
While loops	O(n^2)	O(1)	Alternative loop syntax
String constructor	O(n^2)	O(1)	Cleaner and concise code