Time: 20 ms (61.23%), Space: 24 MB (7.08%) - LeetHub

669-trim-a-binary-search-tree/669-trim-a-binary-search-tree.cpp

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