Solving Techniques

This page is for Classic Sudoku solving techniques. For Variants, see Variant Solving Techniques. The techniques listed here will usually apply when variant constraints are present, but the ways the variants interact with these techniques will change depending on the specific constraint.

Logical Solving Techniques

(Really, all the techniques on this page are "logical" from a certain point of view.)

• Subsets (Hidden and Naked)
  • Singles
  • Tuples (Pairs, Triples, Quadruples, etc.)
  • Basic Fish
• Locked Candidates
  • Pointing
  • Claiming
• Single Digit Techniques
  • Turbot Fish
    • Skyscraper
    • 2-string Kite
  • Empty Rectangle
  • X-Chain
  • Complex Fish
    • Finned Fish
    • Franken Fish
    • Mutant Fish
  • Kraken
• Alternating Inference Chains
  • Wings
    • XY-Wing (aka Bent Triple)
    • W-Wing
    • S-Wing
    • L-Wing
    • M-Wing
  • XY-Chain
  • Continuous Nice Loop (and Discontinuous Nice Loop)
• Almost Locked Sets
  • XYZ-Wing, WXYZ-Wing (aka Bent Quad)
  • Sue de Coq
  • ERI Pair
  • ALS-XZ (including doubly-linked)
  • ALS-XY-Wing (including triply-linked)
  • ALS-W-Wing
• Multiple and Dynamic Forcing Chains
  • Region Forcing Chain
  • Cell Forcing Chain
• Global Techniques ("Exotic")
  • SET Equivalence Theory (see also Phistomefel Ring, Multi-Sector Locked Sets (see also SK Loop), Rank 0 Logic
  • Exocet
    • Junior Exocet
    • Senior Exocet
  • Firework
  • Impossible Pattern Techniques
    • Broken Wing
    • Bivalue Oddagon
    • Trivalue Oddagon

Uniqueness Techniques

• Unique Rectangle
• Unique Loop
• Extended Rectangle
• Bivalue Universal Grave
• Gurth's Symmetrical Placement
• Distinction Theory

Other Techniques

• Trial and Error
• Depth-First Search