The DOMINO puzzle requires only two, easy to understand strategies to reach a solution. Of these, one is laden with pitfalls if you are not very
attentive, while the other is straightforward and very easy to apply.
When specific cells need to be referred to in this discussion, they will be designated as C4-R3 which means the 4th cell in row 3.
Search Strategy.
As the name implies, this strategy requires a very careful search of the puzzle for each individual domino. To assist in this, it is a good idea
to prepare a list of all the dominos you need to find, and to tick them off as you do find them. Here is such a list for this puzzle:-
0-0
0-1 1-1
0-2 1-2 2-2
0-3 1-3 2-3 3-3
0-4 1-4 2-4 3-4 4-4
0-5 1-5 2-5 3-5 4-5 5-5
As you search, you will quickly find that there is more than one location in the puzzle where most of the domonos could be hiding. Keep searching
until you encounter a domino which only appears in one location. The first domino in the list with this characteristic is 0-4. On the first pass through the list five
other unique location can be found, these being 0-5, 1-4, 3-3, 4-4 and 5-5.
Shortcut Strategy
At this point you could do another scan through the list of dominos, but there is an easier way. Look at the cells C1-R5 and C2-R5. The 1-2 domino
could go here, or it could go at C2-R1 and C2-R2. However, because the location C1-R5 and C2-R5 is hemmed in by already inserted dominos, there is no alternative to
placing it here. Four other dominos, viz. 3-5, 1-1, 0-3 and 0-1 can also be inserted in this way.
Alternating between these two strategies will quickly lead to a solution.
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