Hacker News Reader

It would be nice, if they could publish the exact cover. I have written some algorithm that can estimate the number of solutions to an exact cover base on the number of solutions it found and the size of the 'tree' that has been explored.

I could write a program myself to calculate the exact cover, but I guess, it will take me about a day to do so. It would not surprise me if the exact cover will be a few hundred mega bytes (when using one character per position).

View on HN

We haven't actually run the thing to completion. We ran it for a couple days and then stopped after finding tens of thousands of solutions. Might explore again if we have time to improve the solver efficiency.

I did write a program to generate an exact cover. Thr output is a little over 5 megabyte when using a notation that list the indices of the positions that have a 1. I have not yet verified that it is correct. My solver found one solution so far and edtimates that the number of solutions is more than 10^50.

Reply on news.ycombinator.com