# How to solve sudoku - Solving sudoku strategies

These are the strategies used to solve a Sudoku.
There are many different solving sudoku strategies discovered .
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### Advanced Sudoku Strategies - Coloring

Simple Colors
Uses only 2 colors to form a single color cluster.
Multi-Colors | Supercoloring
Uses multiple colors (4, 6 or a higher multiple of 2) to form multiple color clusters.
Weak Colors
Extends Simple-Colors by the use of hinge linkages.
X-Colors
Uses only 2 colors, but also takes the implications for each color into account.
Color Trap
A technique that uses a single cluster to eliminate candidates outside the cluster.
Color Wrap
A technique that uses a single cluster to detect a contradiction in one of the colors.
Color Wing
A technique that uses multiple clusters to eliminate candidates outside these clusters. Same as Multi-Colors.
3D Medusa Coloring | Advanced Coloring
A set of techniques that uses colors on multiple digits.

### Solving Sudoku Strategy - Singles

Full House
A house with a single empty cell.
Last Digit
The last instance of a digit.
Hidden Single | Pinned Digit
A single candidate remaining for a digit in a house.
Naked Single | Forced Digit | Sole Candidate
A single candidate remaining in a cell.

### Advanced Sudoku Strategies - Fish

X-Wing
2 rows vs. 2 columns
Swordfish
3 rows vs. 3 columns
Jellyfish
4 rows vs. 4 columns
Squirmbag
5 rows vs. 5 columns
Finned Fish
Fish patterns with additional candidates in a single box.
Sashimi Fish
Incomplete basic fish patterns with a fin.
Franken Fish
Fish patterns that include box constraints.
Mutant Fish
Fish patterns with mixed sets of constraints.
Kraken Fish
A fish pattern with indirect connections to a candidate which can be eliminated.

### Advanced Sudoku Strategies - Chains and Loops

Forcing Chain
Generic term for any type of chain.
X-Chain
Single digit chain of cells.
XY-Chain
Chain of bivalue cells.
Remote Pairs
Simplified form of XY-Chain, involving only two digits.
Fishy Cycle| X-Cycle
Single digit continuous loop.
Broken Wing
Eliminations caused by loops of odd length.
Nice Loops
Several types of loops formed by cells following strict rules and a notation system.
Double Implication Chain| DIC
There are 2 interpretations circulating. The first originates from a reliable source [1].
A Forcing Chain that has implications in both directions.
2 Forcing Chains starting from a bivalue cell or a bilocal unit showing a verity.
Alternating Inference Chain| AIC
A chain where each node is a candidate, with alternating strong and weak inference.

### Solving Sudoku Strategy - Intersections

Locked Candidates| Intersection Removal | Line-Box Interaction | Pointing (Pair, Triple) | Claiming
Candidates are locked in the intersection of a line and a box.
Locked Pair
A Naked Pair located in a single intersection.
Locked Triple
A Naked Triple located in a single intersection.
Almost Locked Candidates
A box-line intersection where the line or the box contains an Almost Locked Set, and the remaining cells in the line or box outside the intersection does not contain digits from the Almost Locked Set.

### Solving Sudoku Strategy - Subsets

Naked Pair
2 cells with candidates for 2 digits.
Naked Triple
3 cells with candidates for 3 digits.
4 cells with candidates for 4 digits.
Hidden Pair
2 digits with candidates in 2 cells.
Hidden Triple
3 digits with candidates in 3 cells.
4 digits with candidates in 4 cells.

### Solving Sudoku Strategy - Wings

XY-Wing
Three cells with pivot cell XY and two pincer cells XZ and YZ.
XYZ-Wing
Three cells with pivot cell XYZ and two pincer cells XZ and YZ.
WXYZ-Wing
Four cells with pivot cell WXYZ and three pincer cells WZ, XZ and YZ.

### Solving Sudoku Strategy - Single Digit Patterns

Skyscraper
Two parallel strong links, weakly connected at the base.
2-String Kite
Two crossing strong links, weakly connected in a box.
Empty Rectangle
A single-digit technique that makes use of a box whose candidates for that digit are contained within the union of a boxrow and a boxcol.

### Solving Sudoku Strategy - Uniqueness

Uniqueness Test
A set of techniques that avoids the Unique Rectangle deadly pattern.
Bivalue Universal Grave
A set of techniques that avoids the Bivalue Universal Grave deadly pattern.
BUG Lite
A set of techniques that avoids the BUG Lite deadly pattern.

### Solving Sudoku Strategy - Almost Locked Sets

ALS-XZ rule
2 Almost Locked Sets with restricted common digit X perform eliminations for common digit Z.
ALS-XY-Wing rule
3 Almost Locked Sets with 2 restricted common digits Y and Z perform eliminations for common digit X.
Death Blossom
A stem cell of N candidates pointing to N petals, each an Almost Locked Set.
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