I don't understand this problem. As I think, the third sample is the tree from the picture. But I can not understand why, for example, 'the number of the ancestor of this node' for the node #18 is 12? What does it mean, 'the number of the ancestor of this node'?

THank you.

As you can see in a picture, the node #18 connected with the #12 node, and

 - #18 is a child for #12;
 - #12 is a ancestor, farther (mother) of #18.

In phrase "the number of the ancestor of this node" the word "number" should be understood ad index (the index of the node, which is an ancestor for target node).