Diameter of Binary Tree

Given a binary tree, you need 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.

Example:
Given a binary tree

  1
 / \
2   3

/ \

4 5

Return 3, which is the length of the path [4,2,1,3] or [5,2,1,3].

http://www.cnblogs.com/zengzhengda/p/6582037.html

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