can anyone tell me what is the 'problem' with test #5, because I get stack overflow, although I don't declare any local variables in my recursive function (I use a vector to simulate the stack)

I have the same problem ,first!
but I find that test#5 may be not a tree!
for example:
3
0 1 1
1 0 1
1
0 1
so you should use array to record whether a node have been in the stack.

sorry:
the example is
4
0 1 1
1 2 1
2 0 1
1
0 1

But your example is not a tree... there are cicle...

Ancorrect test