In this version, like in a normal sudoku, numbers 1 to 9 appears only once in every row or column. But in the nine 3 X 3 subblocks any number, instead of appearing only once, appears either once or twice or not at all. In each subblock, three numbers appears once, three numbers appears twice & three numbers do not appear at all.
Considering this rule solve the sudoku puzzle given below.
+---+---+---++---+---+---++---+---+---+ | 1 | | 6 || | 7 | || 2 | | 8 | +---+---+---++---+---+---++---+---+---+ | | 1 | || 7 | | 2 || | 9 | 3 | +---+---+---++---+---+---++---+---+---+ | | 7 | || | | 4 || | | | +===+===+===++===+===+===++===+===+===+ | | 8 | 9 || 1 | | 6 || | | 2 | +---+---+---++---+---+---++---+---+---+ | 5 | | || 3 | | || | 1 | | +---+---+---++---+---+---++---+---+---+ | 8 | | 3 || | | 7 || | | 9 | +===+===+===++===+===+===++===+===+===+ | | 6 | || | 9 | || 8 | 3 | | +---+---+---++---+---+---++---+---+---+ | 2 | | 1 || | | 5 || | | 7 | +---+---+---++---+---+---++---+---+---+ | 9 | | || 8 | | 3 || | | 4 | +---+---+---++---+---+---++---+---+---+
