propagate-then-search

When to Use

• Constraint satisfaction problems
• When assigning one value constrains others
• Large search space that can be pruned
• Sudoku, scheduling, puzzles with rules

When NOT to Use

• No constraint propagation possible
• Constraints are independent
• Simple brute force is fast enough

The Pattern

Propagate: When you assign a value, infer all consequences. Search: Only guess when propagation can't proceed.