This is the second in a series about the Sudoku puzzle and some of the solution methods. In the last post the puzzle was defined and the rules for solving were shown. In summary, you have a 9×9 array of squares that have to be filled with numbers such that each row, column and container contain one through nine with no repeats.

In this post we’ll show the method to find the “gimmies,” or numbers that you don’t really have to think very much about. Let’s recall the puzzle…

Recall the container rule that every container must have the numbers one through nine in it. Given that, consider the top three containers which form a group of three rows. Look for two of those containers having the same number in them. Sometimes this combination will define a unique place for that number in the third container. Let’s see an example of where that happens in this puzzle… [Read more…]