0669. Trim a Binary Search Tree.cpp

class Solution {
public:
    TreeNode* trimBST(TreeNode* root, int L, int R) {
        if (!root) return root;
        if (root->val >= L && root->val <= R) {
            root->left = trimBST(root->left, L, R);
            root->right = trimBST(root->right, L, R);
            return root;
        }
        if (root->val < L)
            return trimBST(root->right, L, R);
        return trimBST(root->left, L, R);
    }
};