Sudoku Primer & Complete Reference

Sudoku Techniques

Introduction

Note: the words techniques, tricks, strategies and tools are used interchangeably on these pages.

This page lists different techniques you can use to solve Sudoku puzzles. Some are basic and can be used on easy puzzles and others are more advanced techniques that will help you solve more difficult puzzles. Most of them can be used on all difficulty levels.

Read through all of them to get familiar with them. Then use this page as a reference when you need to brush up on specific techniques. The techniques on this page are ordered roughly from the easiest to the most difficult.

"Hey Joe, do you have a loner cell I can borrow?"
Techniques are “tools” you can add to your “toolbelt” to use when solving puzzles. As your solving skills improve you will find that easier puzzles aren’t as interesting anymore and that you can move on to harder ones.

You will learn many techniques that you can use to solve difficult puzzles. When you have mastered all of these techniques you will be able to solve any puzzle. Note that the hardest puzzles require you to use combinations of techniques, and even then they can be very challenging. But that is when it becomes fun. You really feel a sense of accomplishment when you solve very difficult puzzles.


Tool: Solving a single cell

Each individual cell can be solved independently. That is, if there are enough numbers it can see.

Solving single cells >>

Tool: Row, column and box (container) completion

Rows, columns and boxes are called containers (see glossary). Solving them is a basic strategy for easier puzzles. But it can also be more advanced.

Solving containers >>

Tool: Solving sections

Solving sections can be very productive, yielding many numbers, especially when there are already many cells populated.

Solving sections >>




Tool: Ghost numbers

Ghost numbers can be used in multiple ways. Master this tool and you will be able to solve harder puzzles.

Ghost numbers >>

Tool: Loner cells

Loner cells are the only cell in a box that isn't in a specific row or column. Learning loner cells will help you find numbers quicker.

Loner cells >>

Tool: Identical twins

Identical twins are somewhat rare but when found they can help yield numbers. Read the page on Loner cells before reading this page.

Identical twins >>

Tool: Ambiguity rule

The ambiguity rule helps on more difficult puzzles. It can help you eliminate possible numbers from a cell or a set of cells.

Ambiguity rule >>



Sudoku - the puzzle that addicts