Update 0222.完全二叉树的节点个数.md

problems/0222.完全二叉树的节点个数.md

@@ -814,6 +814,35 @@ impl Solution {
 }
 ```
 
+// 迭代
+```rust
+use std::rc::Rc;
+use std::cell::RefCell;
+use std::collections::VecDeque;
+impl Solution {
+    pub fn count_nodes(root: Option<Rc<RefCell<TreeNode>>>) -> i32 {
+        let mut res = 0;
+        let mut queue = VecDeque::new();
+        if root.is_some() {
+            queue.push_back(root);
+        }
+        while !queue.is_empty() {
+            for _ in 0..queue.len() {
+                let node = queue.pop_front().unwrap().unwrap();
+                if node.borrow().left.is_some() {
+                    queue.push_back(node.borrow().left.clone());
+                }
+                if node.borrow().right.is_some() {
+                    queue.push_back(node.borrow().right.clone());
+                }
+                res += 1;
+            }
+        }
+        res
+    }
+}
+```
+
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