For anyone who’s spent hours twirling the sides of the colored puzzle, this news might just be frustrating. But for mathematicians, this is a big success for elegant computer solutions.
Rubik’s Cubes, in case you forgot about the ’70s sensation, challenge players to spin sides of 3x3x3 cube in order to make each surface a single color.
Last year, students at Northeastern University proved they could solve even the most twisted configuration in as few as 26 moves. In March, Mr. Rokicki one-upped them by whittling down that number to 25. His solution used a computer to churn through possible paths toward victory and filtered out any repeats. This is how most mathematicians solve puzzles nowadays when there are 43 quintillion possible positions – teach a computer to do it, and just wait for it to consider every possibility.
But this takes a really long time. Rokicki sped up the process by finding a clever way to divvy up the possible configurations into sets. It still took his PC 1,500 hours to come up with a solution.