in reply to Powers of three

Neat!

I wouldn't interpolate $a in the for loop. Or 1. Makes me kind of wonder what influenced you to do so.

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Re^2: Powers of three
by simcop2387 (Acolyte) on Feb 07, 2006 at 07:55 UTC
    honestly i don't remember it was written in my statistics class at 9am
    i'm also partially curious as to why the program works, i know what its doing, i worked it out by hand before writing it in perl
      A simple explanation of why it works, since you wondered:
      If you continue your triangle, you end up with this:
                     1
                    1 1
                   1 0 1
                  1 1 1 1
                 1 0 0 0 1
                1 1 0 0 1 1
               1 0 1 0 1 0 1
              1 1 1 1 1 1 1 1
             1 0 0 0 0 0 0 0 1
            1 1 0 0 0 0 0 0 1 1
           1 0 1 0 0 0 0 0 1 0 1
          1 1 1 1 0 0 0 0 1 1 1 1
         1 0 0 0 1 0 0 0 1 0 0 0 1
        1 1 0 0 1 1 0 0 1 1 0 0 1 1
       1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
      1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
      
      You probably see a pattern by now, but if not, change all the 0s to spaces, and all the 1s to #s:
                     #
                    # #
                   #   #
                  # # # #
                 #       #
                # #     # #
               #   #   #   #
              # # # # # # # #
             #               #
            # #             # #
           #   #           #   #
          # # # #         # # # #
         #       #       #       #
        # #     # #     # #     # #
       #   #   #   #   #   #   #   #
      # # # # # # # # # # # # # # # #
      
      No matter how far down you go, you always end up with a triangle, and you can continue by copying that triangle to its bottom left and right sides. This is easy to see, but I can't find the words that actually explain it, so please take a look for yourself if you have doubts about that. Now take a look at this: the first row has 1 as its sum. This triangle-point is copied twice, so the first 2 * 1 rows have 3 * 1 as their sum. This triangle is copied twice, so the first 2 * 2 * 1 rows have 3 * 3 * 1 as their sum. The first 2^3 * 1 rows have 3^3 * 1 as their sum. I'm sure you get the idea by now :)
      It's not proof, but hopefully it's good enough.
      Nice code.

      Logically the state of any point is an XOR of its two parents taking a missing parent to be 0. (and seeding with a 1 at the point)