Background: Sudoku and Pseudoku A Sudoku puzzle consists of 9-by-9 grid of squares, some of them blank, some of them having integers from 1 to 9. A typical Sudoku puzzle will then look something like this: 3 5 8 9 7 8 w 01 1 NI 23 VAWOO 9 3 4 2 1 9 3 6 1 1 5 72 1 8 6 3 4 2 6 7 No 00 NO 9 82 3 5 6 8 7 2 To solve this puzzle, all the squares must be filled with numbers from 1 to 9 such that the following are satisfied: 1. every row has all integers from 1 to 9 (with each appearing only once) 2. every column has all integers from 1 to 9 (with each appearing only once) 3. every 3-by-3 sub-grid, or block (with bold outlines around them going from top-left to bottom-right) has all integers from 1 to 9