Mathturion

The Lamplighter of Rome

“Friends and fellow travelers,” the curator Viarum began, “my challenge is simple to describe, though not so easy to solve. At every crossroads stands a streetlight, connected by roads as shown in the diagram. Beginning from the marked crossroads, the Lamplighter must travel through the streets and light every streetlight exactly once. He must complete the task in fifteen straight-line moves, without retracing his path. Notice that there is no through road near the bottom of the map.”

Starting from the highlighted crossroads (row 7, column 3), light all 64 streetlights in as few straight-line moves as you can. Lighting them all wins; doing it in 15 moves — the fewest possible — is the perfect solution. Each move travels along the streets in one direction and lights every lamp along the way. Note the gap between crossroads (8, 4) and (8, 5) — there is no road there.

Click any crossroads in the same row or column as your current position to move there in a straight line. Every streetlight along the way will light up.