Inverted Pyramid Pattern Algorithm and Example in C#

Following is example of inverted pyramic * pattern with 8 rows:

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

Concept for achieving algorithm

In the above example - if we inspect we can find that '*' count from botton to up as follows:

1. 8th row=> 1 star,
2. 7th row=> 3 stars,
3. 6th row=> 5 stars,
4. 5th row=> 7 stars,
5. 4th row=> 9 stars,
6. 5th row=> 11 stars,
7. 4th row=> 13 stars,
8. ..
9. ...
10. ...  

So it's a odd number series. And odd number series formula will be (2n-1) where n is starting with 1.

Method for generating inverted pyramic pattern

The pattern will be divided into two part:

1. A for loop will be used to print blank spaces
2. A for loop will be used to print odd number series (2n-1)

Algorithm

1. Initialize variables i, j and rows for rows, blank spaces and number of rows respectively.
2. The number of rows here is 8, the user can take any number.
3. Initialize a for loop that will work as the main loop in printing the pattern and drive the other loops inside it.
4. Initialize a for loop that will print the blank spaces inside the main loop.
5. Now, in order to print the star pattern in odd number. To do that, we will initialize a for loop with the condition given as 2 * i – 1, because the number of stars is odd.

Here is example in C#

using System;

namespace ConsoleApp1
{
    public class Program
    {
        public static void Main(string[] args)
        {
            int i, j, rows = 8;
            for (i = rows ; i >= 1; i--)
            {
                // Loop to print the blank spaces
                for (j = rows-i ; j >=1; j--)
                {
                    Console.Write("  ");
                }
         
                // Loop to print the stars
                for (j =  (2 * i - 1); j >=1; j--)
                {
                    Console.Write("* ");
                }
         
                // Move to the next line to complete the pattern
                Console.Write("\n");
            } 
        }
    }
}

You can try online C# editor here: Inverted Pyramid