Palantir Technologies Web Developer interview questions

There is a 3d matrix where a slice would look like this 1 3 4 0 0 1 2 0 0 0 2 4 0 0 0 1 0 0 0 8 0 0 0 1 0 in this slice there are two islands with weights of 9 and 18. Islands can be connected in the 3rd dimensions too (i.e. 3d chunks). Fund the chunk/3d-island with the largest weight (in the most optimal way space- and complexity-wise).