By Eugenie Samuel Reich of Nature magazine
An Irish mathematician has used a complex algorithm and millions of hours of supercomputing time to solve an important open problem in the mathematics of Sudoku , the game popularized in Japan that involves filling in a 9x9 grid of squares with the numbers 1-9 according to certain rules.
Gary McGuire of University College Dublin shows in a proof posted online on January 1 that the minimum number of clues--or starting digits--needed to complete a puzzle is 17; puzzles with 16 or fewer clues do not have a unique solution. [More]
