When examining a Sudoku that presents only one number as a clue throughout the puzzle, you can cross 4 rows and 4 columns (8 numbers are missing). If these four rows and four columns intersect in cells that do not contain the given number, the numbers that appear in cells not crossed by rows and columns can be excluded. Example: (in this one, the number “9” appears only once in cell H2):
Apparently, this solution is for when there is only one number (clue) available in the Sudoku.
Example, for the number “2”
