Super Sudoku

The Sudoku version played on a 9 x 9 squares board, is a well known puzzle game. The goal of the puzzle is for the player to put a digit from 1 to 9 in each free square, so that: (a) in every row of 9 squares, no digit occurs more than once (b) in every column of 9 squares, no digit occurs more than once (c) in every marked 3x3 subsquare, no digit occurs more than once. A given 9 * 9 Sudoku puzzle typically contains some squares that already contain a number from 1 to 9.

See how we mathematically formulate these constraints and solve it, and its big brothers, the Super Sudokus, with Integer Programming in our article on Medium. And how for the bigger problems Gurobi beats CBC beats CPLEX at it.