问题
I have started reading "Think Like A Programmer" by V Anton Spraul. Here is the question.
The train technique mentioned in the book works fine for the example sighted in it. I was attempting to write the train approach method to solve the sliding tiles problem.
Assuming that I am working on subset of the complete problem, for the below set of tiles (as given as example in the book), the approach mentioned works fine.
6 8 .
5 4 7
We move anti-clock wise until we get 4,5,6 in order in top row and then slide 8 over empty space to get all in order.
But for the below, I could not find any suitable method
. 8 6
7 4 5
Is it possible that there can be permutations where the puzzle is unsolvable?
Thanks,
/MS
回答1:
Yes, in fact some puzzles are unsolvable. The way to find out is to try to solve two puzzles at a time: one being the original puzzle, and one being the original puzzle with two tiles switched. When you solve one puzzle, you know that the other one cannot be solved.
来源：https://stackoverflow.com/questions/15733394/regarding-approach-to-solving-sliding-tiles-puzzle