Update 0101.对称二叉树.md

problems/0101.对称二叉树.md

@@ -800,6 +800,39 @@ impl Solution {
 }
 ```
 
+迭代：
+```rust
+use std::cell::RefCell;
+use std::collections::VecDeque;
+use std::rc::Rc;
+impl Solution {
+    pub fn is_symmetric(root: Option<Rc<RefCell<TreeNode>>>) -> bool {
+        let mut queue = VecDeque::new();
+        if let Some(node) = root {
+            queue.push_back(node.borrow().left.clone());
+            queue.push_back(node.borrow().right.clone());
+        }
+        while !queue.is_empty() {
+            let (n1, n2) = (queue.pop_front().unwrap(), queue.pop_front().unwrap());
+            match (n1.clone(), n2.clone()) {
+                (None, None) => continue,
+                (Some(n1), Some(n2)) => {
+                    if n1.borrow().val != n2.borrow().val {
+                        return false;
+                    }
+                }
+                _ => return false,
+            };
+            queue.push_back(n1.as_ref().unwrap().borrow().left.clone());
+            queue.push_back(n2.as_ref().unwrap().borrow().right.clone());
+            queue.push_back(n1.unwrap().borrow().right.clone());
+            queue.push_back(n2.unwrap().borrow().left.clone());
+        }
+        true
+    }
+}
+```
+
 <p align="center">
 <a href="https://programmercarl.com/other/kstar.html" target="_blank">
   <img src="../pics/网站星球宣传海报.jpg" width="1000"/>