leetcode.700 二叉搜索树中的搜索

class Solution {
public:
    TreeNode* searchBST(TreeNode* root, int val) {
       if(root == NULL) return NULL;
       if(root->val > val) return searchBST(root->left, val);
       if(root->val < val) return searchBST(root->right, val);
       return root;  
    }
};