Sudoku Rules

The aim of the puzzle is to enter a numeral from 1 through 9 in each cell of a grid - most frequently a 9×9 grid made up of 3×3 subgrids (called "regions").

A. These are the "columns", and all 9 of them must be filled in with all 9 numbers without repeating any of them.

B. These are called "rows", and as the columns, all 9 numbers need to fit in each cell without being repeated.

C. This is a grid and is called "Region". The same procedure applies to it as well. All 9 numbers with no repetition.

Some cells already contain numbers, known as "givens". The goal is to fill in the empty cells, one number in each, so that each column, row, and region contains the numbers 1 through 9 exactly once.

Each number in the solution therefore occurs only once in each of three "directions", hence the"single numbers" implied by the puzzle's name.