Sudoku Technique No.4 Fitting In - Hard Level

 中文版

Let's continue with Fitting In technique, in Hard level. In Fitting In Medium level, we only used cell as fitters. Why, units can be fitters too!

See the board below, in box 2 we have three empty cells 23, 26 and 29, three missing numbers 4, 6 and 9. We can see there a fitter of 4 in 32, but where is the other fitter?

Look at box 1, although there is no 9 in it, there is a 9 in 42. After pointing 42 to box 1, we know 9 in box 1 must be in 11 or 13, so box 1 can be used as a fitter that fits a 9 into box 2. Now we have two fitters 4 and 9 fit into box 2, the solution: 236. Click the board to see the animations.

Another example of box fitter fitting into column.

Again columns and rows can be unit fitters too, here is a column fitter fitting into column:

Things could get complicated:

More complicated:

Even more complicated:

I will stop here, but believe me, things could get further more complicated because, as pointers relay, fitters relay too.

So there you go, Fitting In technique at Hard level, pointing out then fitting in, which is a hint to my next blog.

 Sudoku Rules and Terminologies
 Technique No.1 Pointing Out - Easy Level

 Technique No.2 Pointing Out - Medium Level
 Technique No.3 Fitting In - Medium Level

 Technique No.4 Fitting In - Hard Level
 Technique No.5 Pointing Out - Hard Level

 Technique No.6 Pointing Out - Expert Level
 Technique No.7 Fitting In - Expert Level

The puzzles in this post are from http://school.maths.uwa.edu.au/~gordon/sudokumin.php The work is licensed under a Creative Commons Attribution 2.5 License. Attribution goes to Gordon Royle and The University of Western Australia.