[Lintcode]二叉树的最大节点

1
/   \
-5     2
/ \   /  \
0   3 -4  -5

3

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