Sudoku Articles

Naked Singles Sudoku Strategy A naked single is an empty cell with only one legal candidate left after checking its row, column, and box. Hidden Singles Sudoku Strategy A hidden single appears when a digit can only fit in one cell within a row, column, or box, even if that cell has several candidates. Naked Pairs Sudoku Strategy A naked pair is two cells in the same unit that contain the exact same two candidates, locking those two digits into those cells. Pointing Pairs Sudoku Strategy A pointing pair or triple happens when every possible location for a digit inside a box lies on the same row or column. X-Wing Sudoku Strategy An X-Wing locks a candidate into the same two columns across two rows, or the same two rows across two columns. Y-Wing Sudoku Strategy A Y-Wing uses one pivot cell and two wing cells to prove that a shared candidate cannot appear in cells that see both wings. Swordfish Sudoku Strategy Swordfish extends X-Wing to three rows and three columns, locking a candidate into a larger line pattern.