LeetCode938. 二叉搜索树的范围和

 1 class Solution {
 2 public:
 3     int sum = 0;
 4     int rangeSumBST(TreeNode* root, int low, int high) {
 5         dfs(root,low,high);
 6         return sum;
 7     }
 8     void dfs(TreeNode* root,int low,int high){
 9         if(root!=NULL){
10             dfs(root->left,low,high);
11             if(root->val >= low && root->val <= high) 
12                 sum += root->val; 
13             dfs(root->right,low,high);
14         }
15     }
16 };