ABC054C

https://gyazo.com/d709f17d39572be0e97aa653b895f2fe

https://gyazo.com/dfc5b8b3a15d7b70e7ca6c8340950de9

Thoughts.

The number of vertices is 8, so it's OK to search all of them in the factorial.

I usually have graphs with adjacency lists, but this time it's an adjacency matrix.

For each permutation, just check "Does it have an edge?

If there's no edges along the way, it's impossible to search ahead, so I'd prefer to use depth-first search to prune the branches.

Official Explanation OK

I'm assuming the solution above, but bit DP says it's O(N^2 2^N).

You have the number of cases where you start at point X for all subsets, follow them all, and end at point Y.

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