How to Solve a Sudoku Puzzle, Step by Step
The fastest way to learn sudoku is to watch a puzzle get solved. Here is a real one, start to finish, using only three kinds of moves. It’s played in color, and every move works the same with numbers.
The short version
Find a cell that only one color can fill, place it, and repeat. Three checks find those cells: follow one color across the board, count the colors around one empty cell, and finish any row, column or block with one cell left.
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Look the board over
This puzzle starts with 30 bubbles. Every row, column and block already has a few, and each still needs the rest of the nine colors. Nothing here needs a guess: every empty cell can be proved one at a time.
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Follow one color
Take Light Purple. It already sits in the second and third rows, and in the fourth and fifth columns. Now look at the top-middle block, which still needs a Light Purple. Every open cell in it is in one of those rows or columns except one. Light Purple goes there.
Lesson: Hidden Single: Last Remaining
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Count around one cell
A few moves later, look at the top-right cell of the middle-left block. Its row, its column and its block hold eight different colors between them. The only one missing is Dark Purple, so Dark Purple goes there.
Lesson: Obvious Single: Last Possible
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Finish what’s nearly full
As the board fills, rows, columns and blocks get down to one empty cell. The third column here has eight colors and one gap. Orange is the one it’s missing.
Lesson: Full House
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Repeat until it’s solved
That’s the whole solve: 51 moves, every one of them one of these three. Each new bubble opens up the cells around it, so the moves come faster near the end. Harder puzzles add notes and patterns, but they still start exactly like this.
Solve one yourself
Most Easy and Medium boards need nothing more than these three moves.
Also on the App Store and Google Play.