Solution Techniques

Solving basic Hadoku is not very different from Sudoku. If an area has just a single empty field, fill in the missing number. If it has multiple missing fields try to eliminate possibilities by looking at neighboring fields. If a field is down to a single possibility, fill it.

Below is the complete list of more advanced solving techniques.

Intermediate Solution Techniques

Arrow - Hidden Subset - Triangle

Advanced Solution Techniques

Box - Linked Pair - Unique Solution - Cycle Contradiction - Chain Contradiction