Merge pull request youngyangyang04#1813 from fwqaaq/patch-25

Update 0538.把二叉搜索树转换为累加树.md

Author: youngyangyang04

problems/0538.把二叉搜索树转换为累加树.md

@@ -375,6 +375,55 @@ object Solution {
 }
 ```
 
+## rust
+
+递归：
+
+```rust
+impl Solution {
+    pub fn convert_bst(root: Option<Rc<RefCell<TreeNode>>>) -> Option<Rc<RefCell<TreeNode>>> {
+        let mut pre = 0;
+        Self::traversal(&root, &mut pre);
+        root
+    }
+
+    pub fn traversal(cur: &Option<Rc<RefCell<TreeNode>>>, pre: &mut i32) {
+        if cur.is_none() {
+            return;
+        }
+        let mut node = cur.as_ref().unwrap().borrow_mut();
+        Self::traversal(&node.right, pre);
+        *pre += node.val;
+        node.val = *pre;
+        Self::traversal(&node.left, pre);
+    }
+}
+```
+
+迭代：
+
+```rust
+impl Solution {
+    pub fn convert_bst(root: Option<Rc<RefCell<TreeNode>>>) -> Option<Rc<RefCell<TreeNode>>> {
+        let mut cur = root.clone();
+        let mut stack = vec![];
+        let mut pre = 0;
+        while !stack.is_empty() || cur.is_some() {
+            while let Some(node) = cur {
+                cur = node.borrow().right.clone();
+                stack.push(node);
+            }
+            if let Some(node) = stack.pop() {
+                pre += node.borrow().val;
+                node.borrow_mut().val = pre;
+                cur = node.borrow().left.clone();
+            }
+        }
+        root
+    }
+}
+```
+
 
 <p align="center">
 <a href="https://programmercarl.com/other/kstar.html" target="_blank">