Sudoku Candidate Elimination Guide

Sudoku Candidate Elimination Guide (Complete Logical Breakdown)

Sudoku mastery is candidate management. Every strong solve is built on eliminating impossibilities until only valid placements remain.

What candidates are

Candidates are digits that can legally fit in a cell based on row, column, and box constraints.

The four layers of elimination

1) Direct elimination (row/col/box)

2) Cross-constraint elimination (box-line interactions)

3) Group elimination (pairs/triples)

4) Cascading elimination (chain reactions)

A structured elimination workflow

• Do a full direct sweep
• Check box-line restrictions
• Search for pairs/triples
• Re-check for cascades
• Repeat

Common mistakes

• Not updating candidates
• Eliminating without verifying constraints
• Ignoring ripple effects after eliminations

Practice drills

• Elimination-only mode (no placements for 5 minutes)
• One-number sweep across all boxes
• Review solved puzzles to identify key elimination moments

Final thoughts

Placement is the result; elimination is the process. Clean candidate elimination makes patterns visible and turns “stuck” boards into solvable ones.