Diameter of a tree

 Problem: Given edges for a tree find the diameter of the tree or the longest path in the tree.

Sample Input: 

4

5 1

1 3

1 2

2 4

Representation of tree: Tree can be represented in multiple ways, 

1. If we simplify the problem and say it is a binary tree we can represent it as array where a[i]-> left is a[2*i] and a[i]->right is a[2*i+1]. 

2. One other way to represent it is by using parent array: parrent[i] = j if there is an edge j->i but the tree needs to be directed in this case

3. We can have a struct/class Node which has pointers to left and right

Node { 

    int val, 

    Node* left, 

    Node* right

}

To calculate the diameter of a tree we have to pick a root and do dfs/bfs to find the left node with maximum distance and find the farthest node from it.