Is Guessing necessary?

Here are a few thoughts on whether you can always solve a Sudoku by logic – ie. without having to resort to guessing.

The answer is that for most simple puzzles simple (or fairly complex) logic will solve the puzzle, but for more difficult puzzles you will need to guess for at least one square – after which you should be able to fall back on good ol’ logic to finish the puzzle.

The Sudoku Programmers forum gives you a few different methods for guessing (gee, and I thought it was just ‘think of a number…’). Like X-Wings, Nishio, Swordfish and Jacko!


I feel a little embarrassed! I (almost) completely misunderstood what I was reading when I researched the topics above!

Yes, Nishio is the word for when you make a guess in Sudoku, then back-track if you need to if you hit a dead-end.

But X-Wings, Swordfish and Jacko are different patterns of numbers that appear in the puzzles, each one with a specific way of solving them. Stay tuned for a future post when I have got my head around them enough to introduce them properly!

Have Fun!


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