Given an arbitrary unweighted rooted tree which consists of N (2 <= N <= 40000) nodes.
The goal of the problem is to find largest distance between two nodes in a tree.
Distance between two nodes is a number of edges on a path between the nodes (there will be a unique path between any pair of nodes since it is a tree).
The nodes will be numbered 0 through N - 1.
The tree is given as an array P, there is an edge between nodes P[i] and i (0 <= i < N).
Exactly one of the i’s will have P[i] equal to -1, it will be root node.
Input:
P = [-1, 0, 0, 0, 3]
Tree looks like this:
0
/ | \
3 1 2
/
4
Output: 3 (one of the longest path is 4 -> 3 -> 0 -> 2).