添加0222.完全二叉树的节点个数迭代解法Java代码

problems/0222.完全二叉树的节点个数.md

@@ -204,7 +204,27 @@ class Solution {
     }
 }
 ```
-
+```java
+class Solution {
+    // 迭代法
+    public int countNodes(TreeNode root) {
+        if (root == null) return 0;
+        Queue<TreeNode> queue = new LinkedList<>();
+        queue.offer(root);
+        int result = 0;
+        while (!queue.isEmpty()) {
+            int size = queue.size();
+            while (size -- > 0) {
+                TreeNode cur = queue.poll();
+                result++;
+                if (cur.left != null) queue.offer(cur.left);
+                if (cur.right != null) queue.offer(cur.right);
+            }
+        }
+        return result;
+    }
+}
+```
 ```java
 class Solution {
     /**