LintCode 二叉树的最大节点

class Solution {
public:
/**
* @param root the root of binary tree
* @return the max node
*/
int maxx=-99999;
TreeNode *nmax;
void max(TreeNode *root)
{
if(root==NULL)
return ;
if(root->val>maxx)
{
maxx=root->val;
nmax=root;
}
max(root->left);
max(root->right);
}
TreeNode* maxNode(TreeNode* root) {
// Write your code here
if(root==NULL)
return NULL;
max(root);
return nmax;
}
};