Sudoku HowTo

Unit or Container

A Unit or Container is a group of cells that are related on the Sudoku puzzle. A unit is either one row, one column or one box in a Sudoku puzzle.

A Sudoku puzzle can have one and only one of each value in each unit.

In Figure 1 the grey cells show a row unit, the green cells show a column unit and the red cells show a box or block unit.

Once a puzzle is completed there has to be one of each value in each unit. There cannot be more than one instance of any value in a unit and each unit has to contain all values.

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Copyright © 2007 - 2018 John Ironmonger
This page last updated on March 24, 2015