Algorithm 3. Surrounding nodes
1	A$\leftarrow \varnothing$; nnearest ← nnearest;
2	B ← Extending nodes(S);
3	for each nref ∈ B do
4	if nref ∈ Ssur(nnearest, ngoal) then
5	A ←A ∪{ nref };
6	end if;
7	end for
8	Return A;