連結：https://leetcode.com/problems/search-in-a-binary-search-tree/

題目：BST的查詢，直接查詢即可。

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