How do I make a Ruby method that makes a diamond of asterisks with 'n' width?

Question

I'm trying to make a method that returns a string that looks like a diamond shape when printed on the screen, using asterisk (*) characters. I want to remove any trailing characters and each line to be terminated with a (\n). I also want it to return nil if the input is an even number or negative, as it is not possible to print a diamond of even or negative size. For example

       *
n=3   ***
       * 

        *
       ***
n=5   *****
       ***
        *

or in other words

"  *\n ***\n*****\n ***\n  *\n"

Method looking something like this:

def diamond(n)
  
end

Can anyone help? Thanks!

Answer 1

Another solution:

def diamond(n)
  return nil if n.even? || n.negative?
  
  diamond_string = ""
  n.times do |i|
    space_count = (i - n / 2).abs
    asterisk_count = n - space_count * 2
    diamond_string << [' ' * space_count, '*' * asterisk_count].join + "\n"
  end

  return diamond_string
end