ABC Puzzles

ABC Puzzles: as easy as A, B, C...

The ABC puzzle is a fun puzzle, and if you haven't come across it, here's how to play:

You start with a grid that can be of any size; usually it is 5 x 5 making this a nice and small, compact puzzle, however it could be larger and 7 x 7 is not uncommon.

There are a variety of different rules that can be used with ABC puzzles. Sometimes the puzzle literally has A, B, C and two blanks, marked with an 'X'. In other versions that you see there will be A, B, C and D in the 5 x 5 version and one blank.

The second version is seen most commonly so is the version I will discuss here.

In an ABC puzzle, each line (both across and down) must have each of A, B, C, D and a blank (X) once and once only.

Unlike puzzles such as sudoku, there are no givens within the grid itself, however you are instead told which letter must appear first within each row or column. Sometimes there will be a number next to the letter, which indicates where that letter must come in the row or column if not first - so 'B2' could mean that the B is the second letter that you encounter in that row or column.

A valid ABC puzzle has one solution only that can be reached through logic.

The main 'what if' is to use the clues that say where a letter must go first in a row or column. You know that row or column must either start with a 'X' followed by that letter, or start with that letter. Therefore by looking at any constraints on the second cell you can often start to place cells straight away.

Focus attention at the start on any cells that have two constraints on them; many puzzles have one cell that this applies to at the start so if the one you are tackling does, then this is a great place to start.

For instance, imagine that the bottom left cell has C1--> to the left of it and C2 underneath it.
__
C1 | |
C2

Now we can see here that, taking the row, the possible values are X or C. From the vertical position however, we see that C must come second, therefore the possible candidates are A,B,D,X. Now the only common value is the 'X' and therefore we know that the bottom left cell must be an X. And we also know therefore that the second cell in from the bottom left must be the 'C'.

Here is a sample puzzle for you. Remember each row and column must contain A, B, C, D and a space (X) once only. Good luck!

ABC Puzzles

Author: Dan

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Last Updated: Oct 10th 2006

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