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].

Note: The length of path between two nodes is represented by the number of edges between them.

Solution:

MAX-DEPTH

class Solution {
public:
    int depth(TreeNode* root){
        if(root == NULL) return 0;
        return max(depth(root->left), depth(root->right))+1;
    }
    
    int diameterOfBinaryTree(TreeNode* root) {
        if(root == NULL) return 0;
        return max(max(diameterOfBinaryTree(root->left), diameterOfBinaryTree(root->right)), depth(root->left)+depth(root->right));
    }
};