Techniques

💡

First tips

In this first lesson we will present some useful tips for solving sudokus.

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▦

Basic method

The simplest way to discover a number is when in a row, column or quadrant there is only one number left to place. In this case the missing number goes in the only empty cell.

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⇄

Cross by row and column

Another way to discover numbers is to make a cross by row and column. This consists of focusing attention on a cell and checking which numbers can go in that position, eliminating those that are in the same row or column.

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🗃

Box line reduction

The box line reduction technique is an advanced strategy that is used when the possible locations of a number in a row or column are entirely within a single region or box.

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🔗

Dual linking

The dual linking technique is applied when two numbers can only go in two cells of a row, column or block, and these cells do not contain other numbers.

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🔍

Hidden Pairs

When two digits can only go in the same two cells of a unit, those cells must hold that pair — clearing every other candidate from them.

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☰

Naked Triples

Three cells in a unit that together use only three candidates lock those digits between them, removing them from the rest of the unit.

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👁

Hidden Triples

When three digits can only go in the same three cells of a unit, those cells reduce to that trio — every other candidate is cleared from them.

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✕

X-Wing

When a digit is confined to the same two columns in two rows, it forms a rectangle and can be removed from those columns elsewhere.

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🧭

Swordfish

The Swordfish technique is used in sudokus when a specific number appears as possible in exactly three rows and three columns.

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⋔

XY-Wing

A two-candidate pivot links two pincer cells that share a third digit, which can then be eliminated from any cell both pincers see.

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XYZ-Wing

XYZ-Wing focuses on finding three cells that form a connection, where two have two possible numbers and the third (pivot) shares a number with each of the other two.

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🏙

Skyscraper

A single-digit pattern: a digit is a conjugate pair in two rows that share a base column, eliminating it from any cell that sees both roof cells.

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🪼

Jellyfish

The four-line extension of the swordfish: a single candidate confined to the same four columns across four rows.

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🅦

W-Wing

Two cells with the same two candidates, linked by a strong link on one of them, eliminate the other candidate from any cell that sees both.

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