sudokUI › Sudoku techniques › Locked Candidates (Claiming)
Locked Candidates (Claiming) in sudoku
Box/Line Reduction · 1-fish: line onto box · how it fits
Within one row or column, every candidate for a digit X lies inside the same box, in two or three cells.
Why it works
The row or column must contain X, and every place for it is inside one box, so the X of that box must lie in that row or column. X is eliminated from the cells of the box outside that row or column.
How to spot it
Go through a row or column digit by digit: when a digit's candidates all fall in one box, check the rest of that box.
Worked example
Locked Candidates (Claiming): in row 1, digit 5 is confined to box 2, so it can be removed from the rest of the box. So 5 is removed from r2c5.
Practise it on a real puzzle. sudokUI generates a puzzle that needs Locked Candidates (Claiming) and takes you straight to the position where it applies. Hints draw the pattern on the board and explain the step.
Practice Locked Candidates (Claiming)Open in the app's guide
In a puzzle's rating
Each time the solver needs Locked Candidates (Claiming), the puzzle's difficulty rating grows by 50. Its class is Medium. It is needed in 17% of puzzles that sudokUI generates. How the rating works.