Merge pull request #1738 from Jack-Zhang-1314/patch-8

update 二叉树的迭代遍历.md about rust

problems/二叉树的迭代遍历.md

@@ -640,6 +640,60 @@ object Solution {
   }
 }
 ```
+
+rust:
+
+```rust
+use std::cell::RefCell;
+use std::rc::Rc;
+impl Solution {
+    //前序
+    pub fn preorder_traversal(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<i32> {
+        let mut res = vec![];
+        let mut stack = vec![root];
+        while !stack.is_empty() {
+            if let Some(node) = stack.pop().unwrap() {
+                res.push(node.borrow().val);
+                stack.push(node.borrow().right.clone());
+                stack.push(node.borrow().left.clone());
+            }
+        }
+        res
+    }
+    //中序
+    pub fn inorder_traversal(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<i32> {
+        let mut res = vec![];
+        let mut stack = vec![];
+        let mut node = root;
+
+        while !stack.is_empty() || node.is_some() {
+            while let Some(n) = node {
+                node = n.borrow().left.clone();
+                stack.push(n);
+            }
+            if let Some(n) = stack.pop() {
+                res.push(n.borrow().val);
+                node = n.borrow().right.clone();
+            }
+        }
+        res
+    }
+    //后序
+    pub fn postorder_traversal(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<i32> {
+        let mut res = vec![];
+        let mut stack = vec![root];
+        while !stack.is_empty() {
+            if let Some(node) = stack.pop().unwrap() {
+                res.push(node.borrow().val);
+                stack.push(node.borrow().left.clone());
+                stack.push(node.borrow().right.clone());
+            }
+        }
+        res.into_iter().rev().collect()
+    }
+}
+```
+
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