Lego robot completes Sudoku puzzles

Lego Mindstorms robots are futuristic toys for creative sprogs. But Swedish programmer Hans Andersson bought a programmable Mindstorms NXT kit for his two daughters and then began tinkering with it himself. The result is a toy that can autonomously solve Sudoku puzzles in what looks like a matter of minutes.

The 'Sudoku Solver' scans the entire puzzle with a light sensor before determining the missing digits in each square. Its computer performs image processing with a thresholding algorithm to make sense of the sensor data. Recognising the existing numbers in the puzzle seems to be the most difficult part of the process.

Working out the missing numbers is easy with a backtracking algorithm, according to Andersson. "But, since the Mindstorms processor is rather slow and since it doesn't allow for recursive functions, it took some care to optimise it," he wrote on his Web site.

Andersson has also created a Mindstorms robot called 'Tilted Twister' that can autonomously solve a Rubik's Cube in about 6 minutes.