# Build a path (or circuit) from the vertex `start` that visits every edge exactly once.
	#
	# ~~~
	# var g = new HashDigraph[Int]
	# g.add_arc(1, 2)
	# g.add_arc(2, 3)
	# g.add_arc(3, 4)
	# assert g.eulerian_path(1) == [1, 2, 3, 4]
	# ~~~
	fun eulerian_path(start: V): Array[V]
	do
		var visited = new HashDigraph[V]
		visited.add_graph(self)
		return visited.remove_eulerian_path(start)
	end