Learn to Solve Sudoku the Dreamagic Way is a Dream Machine Site The Dream Machine --- The Imagination of the World Wide Web

Picking Cherries - the Ripe Ones

This lesson will introduce you to finding and filling "singletons"...that is, those squares where...usually...simple logic tells you that only one number could possibly fit. The puzzle used for this demonstration is itself simple. Further lessons will involved more difficult puzzles, and thus more difficult logic. The only logic necessary is simple elimination...either isolating the only square where a particular number will fit...or isolating the only number that might fit into a particular square. The former is generally easier to visualize, so use it as much as possible in this exercise.

Here are two key facts to ALWAYS keep in mind when solving a Sudoku puzzle.

Every square in the puzzle intersects with exactly one row, one column and one box.
No number can be placed in a square if that number already appears in the same row, the same column or the same box as that square.

We strongly suggest that you turn on the F3 function to help you solve this, and all other Suduko puzzles. It will inform you which numbers are still needed in each row, column and box in the puzzle as long as there are fewer than 6 numbers still needed. If 6 or more are still unfilled, no information is provided. The F4 function will show them all, but we have found that this is "too much information" for most cases. However, turn it on so you can see the full layout, then turn it off again...by clicking the F4 icon again. The F3 function will help you decide where to look next for possible aqua res to be filled. The only potentially confusing thing about the layout is the ovals, which contain information about the boxes. The ones at the top and bottom relate to the boxes immediately below or above them respectively. The ones near the left margin are for the central boxes, top to bottom relating to left to right in the layout.

By the way, this function can be easily duplicated for paper and pencil solutions. Writing even part of this layout along the sides of the puzzle will help you a lot, especially with the harder puzzles.

Here are some hints for this solving this first puzzle.

It will NEVER be necessary for you to GUESS what number goes into a square for this puzzle.

After you turn on the F3 function, look in rows, columns or boxes that have the FEWEST NUMBERS still missing.

Start by looking for squares that "need" a 1. Then look for those needing a 2. And so on. In the puzzle below, for example, it is easy to see that a 3 must go in the 6th row and fifth column, since the 4th and 5th rows already contain a 3 and the box does not. A 9 is similarly easy to place in the central box. Watch what happens to the F3 display as you enter these numbers.

If you get stumped after entering some numbers, turn on the F1 function. The program will show you which singletons...ripe cherries...still remain to be filled...picked. Unfortunately, it is not always easy to see how the computer arrived at its conclusions, since it can "look ahead" much further than you or I. However, this can be helpful if you have eliminated most of the easy ones. You could also turn on the F2 function and look at them one at a time.

One final hint. Sometimes, when you have eliminated all but two possibilities for a particular row, column or box, even though you don't know where each number goes, the mere fact that those two numbers MUST go into the two remaining squares, can help you deduce where the rest go in the other rows, columns or boxes. ENJOY!