Update 0701.二叉搜索树中的插入操作.md

problems/0701.二叉搜索树中的插入操作.md

@@ -677,6 +677,30 @@ impl Solution {
 }
 ```
 
+递归：
+
+```rust
+impl Solution {
+    pub fn insert_into_bst(
+        root: Option<Rc<RefCell<TreeNode>>>,
+        val: i32,
+    ) -> Option<Rc<RefCell<TreeNode>>> {
+        if let Some(node) = &root {
+            if node.borrow().val > val {
+                let left = Self::insert_into_bst(node.borrow_mut().left.take(), val);
+                node.borrow_mut().left = left;
+            } else {
+                let right = Self::insert_into_bst(node.borrow_mut().right.take(), val);
+                node.borrow_mut().right = right;
+            }
+            root
+        } else {
+            Some(Rc::new(RefCell::new(TreeNode::new(val))))
+        }
+    }
+}
+```
+
 
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