C How to Program, Fifth Edition

Appendix E. Game Programming: Solving Sudoku

Introduction

The game of Sudoku exploded in popularity worldwide in 2005. Almost every major newspaper now publishes a Sudoku puzzle daily. Handheld game players let you play anytime, anywhere and create puzzles on demand at various levels of difficulty.

A completed Sudoku puzzle is a 9×9 grid (i.e., a two-dimensional array) in which the digits 1 through 9 appear once and only once in each row, each column and each of nine 3×3 grids. In the partially completed 9×9 grid of Fig. E.1, row 1, column 1, and the 3×3 grid in the upper-left corner of the board each contain the digits 1 through 9 once and only once. Note that we use C’s two-dimensional array row and column-numbering conventions, but we’re ignoring ...