Pattern recognition:
- Visit every vertex once = Hamiltonian path
- Graph is implicit (knight move graph)
- vertices, too many for bitmask DP ()
Solution: Backtracking with Warnsdorff's heuristic.
Warnsdorff's rule: From current position, move to the square with the fewest onward moves (lowest degree among unvisited neighbors).
This greedy heuristic dramatically reduces backtracking and usually finds a solution quickly.