# Disables all core updates. Added by SiteGround Autoupdate: define( 'WP_AUTO_UPDATE_CORE', false ); Solving Sudoku Puzzles | Don's Roost

Solving Sudoku Puzzles

The digital revolution has brought about many changes in our lifestyles. Our computing devices are quickly replacing the traditional printed media of newspapers, books and magazines. Only a few years ago, Sudoku puzzles were invented and published in the printed media. While they were, and still are, very popular they suffered from the requirement of the use of a pencil and eraser. Puzzles on a printed page could become very messy very quickly. Only the bravest of solvers would attempt to solve a puzzle with an ink pen. The migration of these puzzles to computers, and now tablet computers, has eliminated this problem. This article will NOT provide instruction in the various puzzle solving techniques. It WILL give you a study plan on learning the techniques and put you on a path to becoming an advanced solver if not an expert. I have seen ads on the Internet offering, at a price, video instructions for this. This puzzles me (no pun intended) as you can only learn by practice whether you watch a video or read printed material. There is no point in paying for the training when it is available for free.

A Sudoku puzzle consists of a 9×9 grid of cells sectioned into 9 3×3 blocks. When completed, each row, column, and block will contain the digits 1 through 9 once and only once. Many cells are left empty for the solver to find but enough are already filled in so that a unique solution exists. Although using numerical digits to distinguish the cells only logic, and no calculation, is used to solve the puzzle. In fact some Soduko puzzles replace the digits with colors to emphasize this. The solution begins by examining the peers of a vacant cell. This consists of all the other cells in  its row, column, and block. Any digit (or color) not occurring amongst the peers is a candidate for the cell. A good way to begin a puzzle is to select a row, column or block for which many of the peers are given and pencil in the remaining candidates. As the solution progresses penciled candidates will be eliminated until only one remains. 

Sudoku puzzles are rated by difficulty. The names given to difficulty levels vary but the beginning solver will quickly discover that some puzzles are easier to solve than others, and some are so difficult that the solver uses trial and error as a last resort. One might think that the more difficult puzzles start out with fewer cells (the “givens” or “clues”) filled in. Actually the difficulties arise as known “patterns” or techniques fail to match the puzzle. It is often the case that a puzzle is half completed when it becomes difficult to solve. The best way to learn the “patterns” is to discover them yourself through practice. The key to learning is really simple. Begin by tackling puzzles that are rated “easy” or “simple”. Solve enough puzzles until that skill level is no longer challenging to you. Then progress to the next level that might be called “medium” or “moderate”. As you progress, you will learn more and more patterns. Soon you will be ignoring puzzles rated at the easier levels.

There is an iOS (Apple devices) app called Sudoku Takeout. It has four difficulty levels.. easy, meduium, hard and evil. I used this app for most of my learning. I started at the easy level and before playing at the evil level I solved over 200 puzzles. The evil level is a bit of a misnomer. Many of the puzzles are at best of medium or hard difficulty. However I have encountered a few that truly live up to the name to the point where I have entered them into another app with a “newspaper” mode discussed below.

At some point it will help to read a printed guide. You will find an excellent one at www.sudocue.net. Here you will be able to put a name to the patterns that you discovered yourself and to learn a few that you did not. The list of patterns documented here is quite extensive. The content probably goes beyond any video that you might purchase and it is provided at no cost. You might want to print it out for reference. Another site that you will certainly want to visit is www.enjoysudoku.com. At this site not only will you find extensive instructions but you will be able to solve actual puzzles at a difficulty level of your choosing. What I really like about this site is the ability to get hints for the more difficult puzzles. The hints, when I have needed them, taught me a few advanced  techniques. The site developer (Jason Linhart) has also published Sudoku apps for various platforms including Mac OS X, iOS, WebOS, and Android.

Some of the Sudoku apps feature a “newspaper or magazine” mode. This allows you to copy the “givens” from a puzzle published in printed media. Combined with an app by Mr, Linhart that provides hints, you can solve nearly any Sudoku puzzle on the planet. This brings up another challenge. Sudoku apps provide enough options to make solving too easy. The challenge (and fun) lies in your ability to solve the puzzle without them. Most apps have an “autofill” feature that will fill in all the possible candidates for the vacant cells. Personally, I do not use this feature. Correctly resolving the candidates is part of the puzzle. Also, you will find that as the candidates are entered, patterns will be seen, and you will enter the solution to many cells long before all candidates are determined.

Finally, in a really difficult puzzle, if you must resort to trial and error, use an app with an “undo” feature. You will soon know that an error exists when no candidates remain for a cell. Then, hitting the “undo” button back to the point where you made the wring guess will allow the solution to proceed normally.

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