int mxheight(Node* root)
{
    if(root==NULL) return 0;
    return max(mxheight(root->left), mxheight(root->right))+1;
}
class Solution {
  public:
    // Function to return the diameter of a Binary Tree.
    int diameter(Node* root) {
        // Your code here
        if(root==NULL) return 0;
        int p=mxheight(root->left)+mxheight(root->right)+1;
        return max(p, max(diameter(root->left), diameter(root->right)));
    }
};