DETAILED NOTES ON SUDOKU HARD - HARD SUDOKU

Naked and hidden singles are the simplest squares to solve. A naked one is when a variety can only go in one feasible mobile. A hidden single is when You can find only cell for your supplied candidate.​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​â€