Trim a Binary Search Tree

<-E 669> Trim a Binary Search Tree

/**
 * 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==nullptr) return root;
        root->left = trimBST(root->left,low,high);
        root->right = trimBST(root->right,low,high);
        
        if(root->val < low){
            return root->right;
        }else if(root->val > high){
            return root->left;
        }
        
        return root;
    }
};