diff --git a/src/problem/mod.rs b/src/problem/mod.rs
index bc02c4c..396b8e9 100644
--- a/src/problem/mod.rs
+++ b/src/problem/mod.rs
@@ -147,4 +147,5 @@ mod p114_flatten_binary_tree_to_linked_list;
 mod p112_path_sum;
 mod p129_sum_root_to_leaf_numbers;
 mod p124_binary_tree_maximum_path_sum;
-mod p173_binary_search_tree_iterator;
\ No newline at end of file
+mod p173_binary_search_tree_iterator;
+mod p222_count_complete_tree_nodes;
\ No newline at end of file
diff --git a/src/problem/p222_count_complete_tree_nodes.rs b/src/problem/p222_count_complete_tree_nodes.rs
new file mode 100644
index 0000000..1edd9e2
--- /dev/null
+++ b/src/problem/p222_count_complete_tree_nodes.rs
@@ -0,0 +1,67 @@
+/**
+ * [222] Count Complete Tree Nodes
+ */
+pub struct Solution {}
+
+use crate::util::tree::{TreeNode, to_tree};
+
+// submission codes start here
+
+// Definition for a binary tree node.
+// #[derive(Debug, PartialEq, Eq)]
+// pub struct TreeNode {
+//   pub val: i32,
+//   pub left: Option<Rc<RefCell<TreeNode>>>,
+//   pub right: Option<Rc<RefCell<TreeNode>>>,
+// }
+//
+// impl TreeNode {
+//   #[inline]
+//   pub fn new(val: i32) -> Self {
+//     TreeNode {
+//       val,
+//       left: None,
+//       right: None
+//     }
+//   }
+// }
+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 result = 0;
+        let mut queue = VecDeque::new();
+
+        if let Some(root) = root {
+            queue.push_back(root);
+        }
+
+        while !queue.is_empty() {
+            result += 1;
+
+            let node = queue.pop_front().unwrap();
+
+            if let Some(left) = &node.borrow().left {
+                queue.push_back(Rc::clone(left));  
+            };
+
+            if let Some(right) = &node.borrow().right {
+                queue.push_back(Rc::clone(right));
+            };
+        }
+
+        result
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_222() {
+    }
+}