Here is the link to the problem : https://www.quora.com/Can-you-share-some-trickest-coding-questions-that-you-have-faced-in-any-coding-contest/answer/Rishabh-Jain-2492

There is N x M matrix filled with 0 and 1 only, lets say a matrix is special if every 2 x 2 sub matrix in it has two 0’s and two 1’s . Find the total number of special matrices you can have for N x M.

On the hunt of an efficient solution.