【树】938. 二叉搜索树的范围和

题目：

 

 

解答：

 

 

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int rangeSumBST(TreeNode* root, int L, int R) 
    {
        if (root == NULL) 
        {
            return 0;
        }
        if (root->val < L) 
        {
            return rangeSumBST(root->right, L, R);
        }
        if (root->val > R) 
        {
            return rangeSumBST(root->left, L, R);
        }
        return root->val + rangeSumBST(root->left, L, R) + rangeSumBST(root->right, L, R);
    }
};