Given a binary tree, write a program to compute the length of the diameter of the tree.
- The diameter of a binary tree is the length of the longest path between any two nodes in a tree. This path may or may not pass through the root.
- The length of the path between two nodes is represented by the number of edges between them.
Input: Given a binary tree 1 / \ 2 3 / \ 4 5 Output: 3 Explanation: Return 3, which is the length of the path [4,2,1,3] or [5,2,1,3]