5 3 3 3 2 6 5 0 6 6 2 0 5 4 1 3 4 4 5 3 6 6 1 5 1 0 6 5 3 5 6 1 1 2 2 4 2 1 1 3 2 5 4 4 3 4 0 6 0 1 2 4 0 0 0 2 |
Source: Submitted by reader Joe Celko. This problem first appeared in the Fifth World Puzzle Championship held in Utrecht (The Netherlands) on 1996 October 15 thru October 20 as a puzzle called DOMINO HUNT (10 points)
+-+---+-+-+ |5|3 3|3|2| | +-+-+ | | |6|5|0|6|6| +-+-+-+ | +-+-+-+-+ |2|0 5|4|1|3|4 4|5| | +---+-+-+ +-+-+ | |3|6 6|1 5|1|0|6|5| +-+-+-+-+-+-+ | +-+ |3 5|6 1|1 2|2|4|2| +---+-+-+-+-+-+-+ | |1 1|3|2 5|4|4 3|4| +---+ +---+ +-+-+-+ |0|6 0|1|2| +-+-+-+-+ | |4 0|0 0|2| +---+---+-+ |
I started by looking for pairs of numbers that only existed once in the whole puzzle. For example, 5-5 can only be found in one place. Using this technique, I found: --> 5-5, 2-5, 2-6, 2-3 In some cases there were more than one occurrence, but they were reduced to one occurrence when other pairs were blocked off. For example once 5-5 is found, there is only one 2-5 left. At this point I could find no other forced pieces, so I had to look into options. I noticed that 3-3 occurred in only 2 spots, both of which included the middle 3 of the top row. I then looked to see if this lead to any limitations, and found that since that middle 3 could not be used to form a 0-3, there was only one 0-3 left (in the lower right). --> 0-3 >From here, there were structural limitations: 0-4 below 0-3 was forced because of the 4 in the corner and so on: --> 0-4, 0-6, 0-0, 2-2, 1-4 At this point there was only one 0-2 left: --> 0-2 Which forced more structural limitations: --> 3-4, 2-4, 4-6, 4-4 I then found a few more forced pieces: --> 0-1, 0-5, 4-5 Which then created more structural limits: --> 5-6, 3-3, 3-6, 1-3, 1-2, 1-5, 1-6, 6-6 And this left only two pieces left: --> 3-5, 1-1 Since all moves were forced, there can be only this one solution to this particular arrangement.