Saturday, 31 December 2011

Puzzle #80: Double Back; Triple Back

Happy New Years Japan, South Korea and the rest of Australia

At least this time I might actually be addressing multiple readers.

For the number 3, Double Back instantly sprang to mind. I had already done it with different numbers in my Four Colour Loop puzzle. I'm not the first to do Triple Back, as it has appeared on Palmer Mebane's blog as well. I like how this one turned out. I think once you get started with this puzzle, it shouldn't cause too many problems.

3. Double Back; Triple Back

Draw a single closed loop through all cells in the grid.  The loop must pass through each boldly marked region exactly thrice.


  1. I liked the opening in the 3x3 box in the corner. But unfortunately I couldn't finish it logically. After 60% I had to use trial-error.

  2. I'm guessing 60% is when you get to the other 3x3 box? Because I think that is the hardest part of the puzzle.
    ROT 13'd: Vg erfbyirf ba gur snpg lbh pna'g unir gjb bar pryy frpgvbaf nf gur erfg bs gur fdhner qbrfa'g erfbyir va n fvatyr cngu gura.

  3. Yeah, I had the bottom part and something in the top-left corner. I realized that the 3x3 box's corner consist the 3rd segment.
    I tried both corner, but I none of them caused contradiction. But I found a solution with some guess.

  4. I found a neat theorem from this puzzle: exactly six (four in Double Back) units of border are crossed from each region. I used this for the other 3x3 box, and apparently it also helped the almost-2x5 rectangle at the top, finishing the puzzle easily afterwards.

    -- chaotic_iak