Have you gotten good at solving Sudokus by straight Scanning? Have you progressed to harder Sudokus where Scanning isn't enough and you sometimes get stuck? Are you interested in learning how to use Candie Markup (pencil marks), or how to use it more efficiently? Then this site was written for you.
There is a Glossary that covers the terminology used on this site. (Sudoku terminology is not really standardized, and some new terms are used here.)
The emphasis in these pages is on Sudoku-solving Tactics which have frequently occurring, easy-to-recognize patterns and which often have big payoffs.
Uniqueness Tactics are thoroughly discussed, with lots of examples given in the pages on Unique Rectangles and BUG+n. The logic behind these Tactics is subtle, but it's worth understanding if you want to be confident that what you're doing makes sense. A full discussion of the issues involved is given in the page on Deadly Patterns.
The two most powerful components of a Sudoku Grid are Pairs and Twins.
Pairs are visually obvious, but Twins are not. The technique of
Twin Tagging is introduced to make Twins
and the relations between them visible. Twin Tagging makes it easy
to develop the notion of a
A Chain, which is sometimes necessary to solve a hard Sudoku, is possibly the most satisfying of all Sudoku Tactics because instead of looking for a set pattern, you construct your own pattern to crack a Worthy Target that you have previously located. In the page on Chains, the ideas are first built up gradually, and then concrete full-Grid examples are given.
For a really hard Sudoku which has thwarted you but nevertheless happens
to contain a
As of 2011 January 7, the Smart Fork page has been completely rewritten to provide a more accurate presentation. The changes involved there gave rise to modifications of several other pages, the Chains page in particular.
No-one's thoughts on Sudoku solving ever really match your own, so you should read over the ideas of as many different people as possible. The Links page will give you a list of references to some helpful Sudoku web sites.
Read Viewing This Site if you are
experiencing any display problems; in particular, see that page
for remarks on using the
If you like what you've seen here and you're registered with one of these services, you can click on its link to bookmark this site:
This page was last updated on 2011 January 7.
The home page for this site is alcor.concordia.ca/~stk/sudoku/
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So this is a complete list of links for the rovers to use: