https://leetcode.com/problems/trim-a-binary-search-tree/
image.png
class Solution {
public:
TreeNode* trimBST(TreeNode* root, int L, int R) {
if (root == NULL) return NULL;
if (root->val < L) return trimBST(root->right, L, R);
if (root->val > R) return trimBST(root->left, L, R);
root->left = trimBST(root->left, L, R);
root->right = trimBST(root->right, L, R);
return root;
}
};
