Sudoku tutorial

Here's a beginner's guide to solving a Sudoku puzzle:

Step 1: Understanding the Sudoku Grid

A standard Sudoku puzzle consists of a 9x9 grid, divided into nine 3x3 boxes. Each box has nine squares, and the entire grid has 81 squares. The puzzle starts with some squares already filled in with numbers from 1 to 9.

The objective of Sudoku is to fill in the remaining empty squares, but there are three important rules:

1. Each row of nine numbers must include all digits 1 through 9 in any order.
2. Each column of nine numbers must also include all digits 1 through 9.
3. And most importantly, each 3x3 box must include all digits 1 through 9.

Step 2: Finding Easy Numbers to Place

Start by finding rows, columns or boxes which already have a lot of numbers filled in. The easiest numbers to place are often in rows, columns, or boxes where there are already 8 numbers filled in. The remaining number will be the one missing number from 1 to 9 that isn't already in that row, column, or box.

Step 3: Using Elimination

For squares where it isn't immediately clear what the number should be, you can use elimination. Look at the numbers already filled in the corresponding row, column, and box. The number that goes in the square will be the one number from 1 to 9 that isn't already present in the row, column, or box.

Step 4: Using the 'Only Choice' Strategy

Sometimes, a square is the only one in a row, column, or box that can possibly contain a certain number. This often happens when a number is already present in 8 of the 9 possible rows or columns that intersect a box. The remaining number must go in the only square in the box where it isn't already in the same row or column.

Step 5: Using the 'Single Possibility' Strategy

If a number has already been placed in all but one of the rows (or columns) that intersect a box, then the remaining row (or column) must contain that number in that box. This can allow you to place a number even when the rest of the row, column, or box is empty.

Step 6: Guessing

If you reach a point where you can't find any numbers to place, and you're sure you haven't made a mistake, it's time to guess. This doesn't often happen in beginner puzzles, but in more advanced ones it's sometimes necessary. Make a guess, but remember where you've guessed so that you can backtrack if it doesn't work out.

Remember, the most important thing when solving Sudoku puzzles is patience. As you get better, you'll start to see patterns and techniques that can help you improve. Happy puzzling!