Modulo Arithmetic

• One of the problems in the 9x9 Sudoku game-board is that the individual cells are labeled 0…80. (In programming one should use "zero-based" rather than "one-based" arrays).

• To address an individual cell you need to know its ROW and COL index

• For this you need to use "modulo arithmetic" and "integer division".

• For example:

i=k\N (integer division)

j= k mod N (modulo arithmethic)

where:

j=COL [0…8]

say:

k=10

i=10\9=1 (truncates to nearest integer)

j=10 mod 9=1 (truncates to nearest integer)

so:

ROW=1 (i.e. 2^nd row)

COL=1 (i.e. 2^nd column)