function Tree-Search(problem, fringe) return a solution, or failure
	fringe <- Insert(Make-Node(Initial-State[problem]), fringe)
	loop do
		if fringe is empty then return failure
		node <- Remove-Front(fringe)
		if Goal-Test(problem, State(node)) then return node
		fringe <- InsertAll(Expand(node, problem), fringe)

function Expand(node, problem) returns a set of nodes
	successors <- the empty set
	for each action, result in Successor-Fn(problem, State[node]) do
		s <- a new Node
		Parent-Node[s] <- node
		Action[s] <- action
		State[s] <- result
		Path-Cost[s] <- Path-Cost[node] + Step-Cost(node, action, s)
		Depth[s] <- Depth[node] + 1
		add s to successors
	return successors