SD Gophers Challange for September (North edition)

Ulam's spirals

Stanisław Marcin Ulam was a mathematician in the early 20th century; who while board at a lecture came started drawing spirals of numbers which later came to bare his name. For this challange we will write a program that will generate the spirals.

A simple example of an ulam spiral: This is a 3x3 squire

   7 8 9
   6 1 2
   5 4 3

Here is another example: 4x4

  13 14 15 16
  12 03 04 05
  11 02 01 06
  10 09 08 07

You can find some greate video's on why Ulam's sprials are cool and how they relate to primes here.

Challenge 1

For this challenge create a program such that:

ulam -d 3

should generate a 3x3 sprial above:

   7 8 9
   6 1 2
   5 4 3

Or

ulam -d 4

should generate a 4x4 sprial above:

  13 14 15 16
  12 03 04 05
  11 02 01 06
  10 09 08 07

Challenge 2

Using a library like termbox-go highlight the prime numbers in a different colors.

Challenge 3

Add another paramater that allow the person to give the starting number, if that number is not provided default to 1.

ulam -s 41 -d 3

should generate a 3x3 sprial above:

   47 48 49
   46 41 42
   45 44 43

Here is a video of someone implementing this using the J programming language.