GIven set of nodes, with pointers only to the parent node, return if the set of nodes can form a tree.

Node is of the form -
struct node { node* parent, int val }

Ex

		10
	1        2
  3	  4     5  6

Input: (6,2), (1,10), (2,10), (3,1), (4,1), (5,2)
Answer: true

Follow up: If the nodes form a tree, return the root of the tree.
Ans: 10