题目链接：https://leetcode-cn.com/problems/trim-a-binary-search-tree/
题目如下：

/*** Definition for a binary tree node.* struct TreeNode {*     int val;*     TreeNode *left;*     TreeNode *right;*     TreeNode() : val(0), left(nullptr), right(nullptr) {}*     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}*     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}* };*/
class Solution {
public:TreeNode* trimBST(TreeNode* root, int low, int high) {if(!root) return nullptr;if(root->val<low){//寻找符合区间的节点TreeNode* right=trimBST(root->right,low,high);return right;}if(root->val>high){//寻找符合区间的节点TreeNode* left=trimBST(root->left,low,high);return left;}root->left=trimBST(root->left,low,high);root->right=trimBST(root->right,low,high);return root;}
};