Thread: designing algorithms

this code below has been copied and annotated from the C++ section,

Code:

using System;


class Test
{
	 
	
	
	static void Main(string[] args)
	{
		int t, space, star; 
			int outer=5;//set final value of control variable 

			//top of diamond - outer loop
			for (t = 1; t <= outer; t++)//control variable t active while  
			{							//less than or equal to outer
				for (space = outer; space >= t; space--)//set control variable 
					Console.Write(' ');//space to outer value
				//while space is greater/or equal to t print space
				for (star = 1; star <= (t * 2 - 1); star++)
					Console.Write('*');
					Console.WriteLine();
			}
			
		
			//bottom of diamond
			for (t = 1; t <= outer - 1; t++)
			{
				for (space = 1; space <= t + 1; space++)//while control variable 
					Console.Write(' ');//space is less than or equal to outer 
									   //control var t + 1 print space
				for (star = 1; star <= outer * 2 - (t * 2 + 1); star++)//7, 5, 3, 1
					Console.Write('*');
				Console.WriteLine();
			}
			
	}
	
}

this program prints a diamond shape, my question is how does one work out the these 2 loops

Code:

for (star = 1; star <= (t * 2 - 1); star++)
	Console.Write('*');
	Console.WriteLine();


for (star = 1; star <= outer * 2 - (t * 2 + 1); star++)//7, 5, 3, 1
	Console.Write('*');
	Console.WriteLine();

previous to seeing this code i had written down a simple flowchart depicting all different stages for each line, as well writing out the sequence of numbers for stars and spaces. is it purely a maths calculation to work out the line...

Code:

for (star = 1; star <= outer * 2 - (t * 2 + 1); star++)//7, 5, 3, 1

or is there a method to this ?

i would have taken forever to get to this without seeing this code, i guess some people are quick problem solvers or they have solved many similar problems

what are your thoughts?