Hidden Triple
Hidden Triple is a digit-position pattern: three digits are limited to three cells within one unit.
Checklist
- Track candidate positions for each digit in one unit.
- Find three digits confined to the same three cells.
- Remove non-triple candidates from those cells.
- Rescan connected units after cleanup.
Place in the Learning Course
Treat this page as a lesson, not only a reference. Check the condition, solve one matching puzzle, then review which candidate or cell made the step valid.
1. Find it
Run the checklist in order until you can explain the pattern.
2. Verify it
Compare the valid and invalid diagrams before removing candidates.
3. Practice it
Open the linked difficulty archive and look for the same condition.
Valid pattern: three digits confined to three cells
Digit confinement allows cell compression and unlocks follow-up placements.
Digit-confinement pattern for hidden triple.
Invalid pattern: one digit leaks outside the set
If any target digit appears outside the three cells, Hidden Triple is invalid.
Digit leakage breaks hidden triple conditions.
Avoid applying it too early
Use this technique only when every checklist condition is true. A board can look similar while still missing one required limit, and removing a candidate too early can break the puzzle later. Before you act, say which unit, which digit, and which cells make the move valid.
- Fix the row, column, or box you are reasoning about before removing candidates.
- Separate candidates that can be removed from candidates that must remain.
- After the removal, rescan for naked singles or hidden singles created by the update.
How to test it in a real puzzle
After reading the article, do not immediately jump to a harder level. Open one linked difficulty archive and look for the same condition while the checklist is still visible. If the pattern does not appear, that is still useful: write down which row, column, box, digit, or candidate set you checked. That note makes the next related technique easier to choose.
Where to use this
Useful in late Medium and early Hard.
Read next
After-Puzzle Review
- Write down one cell or candidate affected by this technique.
- Check whether you almost removed a candidate without the full condition.
- Choose whether to solve one more puzzle at this level or read the related technique first.