Counting Grand Tours — Solution & Editorial

Back to the Problem

Bitmask DP dp[mask][u] = number of paths covering exactly 'mask' ending at u; extend to adjacent unvisited nodes. Sum over full mask and all endpoints.

Complexity: O(2^N · N²)

Watch out: Counts can reach ~14! ≈ 8.7×10¹⁰ — 64-bit.