Mensa Guide to Solving Sudoku

Mensa Guide to Solving Sudoku, by Peter Gordon ★★★
On occasion, I find that Sudoku is a great way to relax and still use the mind. Naturally, over time, one becomes interested in harder puzzles and looks for better algorithms for resolving the puzzle when answers don’t seem to be coming. So, I was quite eager to read this book, since it is supposedly written for really smart people. In actual fact, the book did give me a few insights in resolving some of the more challenging puzzles. Unfortunately, the added insights from the book help only in limited circumstances. He also provides a history of Sudoku, which I found to be quite interesting. I did not realize that Sudoku did NOT come from Japan, but was popularized there.
A combination of the techniques that I have developed as well as techniques of this book can resolve many but certainly not all Sudoku puzzles. Gordon admits that there are puzzles that simply are not solvable without guessing. I was grateful that somebody finally admitted that. He also noted that the Sudoku is written poorly if it eventually demands a guess to solve. My technique involves writing a tic-mark whenever a 9-block unit is reduced to just 2 squares of possibility for a given number. Gordon uses a more conventional tic-mark technique, where the tic-marks include all the possibilities for a given square. Gordon’s technique is best used when solving Sudoku on a computer, as I do not use a pencil, and certainly would object to having to write and erase multiple times. Gordon on paper has the result of taking the joy out of Sudoku. An optimal computer Sudoku game program would show all tic-marks, but show when tic-mark numbers are reduced to only 2 per 9-block unit by changing the color of the tic-marks to easily visualize them. Gordon’s advanced techniques are of value only when the puzzles are nearly completely solved, and not as useful early in a puzzle when most of the unfilled blocks have multiple possibilities. Gordon provides lots of puzzles that demonstrate his techniques, and is easy to read, though certainly not requiring a “Mensa” mentality, which seems to me more an indication of the person’s arrogance rather than their intelligence.