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What does this all mean? ==> Rows, columns and blocks can all be represented with the same data structure! We will use the interface ICellSet to represent the set of cells corresponding to a particular row, column or block. There is also the implication that each cell "knows" which specific row, column and block to which it belongs, so
(In the support class, the Sudoku grid is modeled by an array of Rows. The Row class contains an ArrayList of HashSets, one HashSet of Integers for each square from that row. The HashSet contains possible values for the square.
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