text: /**
   * 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 L, int R) {
          if(root == NULL) {
              return root;
          }
          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;
      }
  };
  