diff --git a/src/problem/mod.rs b/src/problem/mod.rs
index 82e736b..4d1cc51 100644
--- a/src/problem/mod.rs
+++ b/src/problem/mod.rs
@@ -140,4 +140,5 @@ mod p150_evaluate_reverse_polish_notation;
 mod p224_basic_calculator;
 mod p21_merge_two_sorted_lists;
 mod p104_maximum_depth_of_binary_tree;
-mod p100_same_tree;
\ No newline at end of file
+mod p100_same_tree;
+mod p226_invert_binary_tree;
\ No newline at end of file
diff --git a/src/problem/p226_invert_binary_tree.rs b/src/problem/p226_invert_binary_tree.rs
new file mode 100644
index 0000000..fab6b4f
--- /dev/null
+++ b/src/problem/p226_invert_binary_tree.rs
@@ -0,0 +1,61 @@
+/**
+ * [226] Invert Binary Tree
+ */
+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;
+impl Solution {
+    pub fn invert_tree(root: Option<Rc<RefCell<TreeNode>>>) -> Option<Rc<RefCell<TreeNode>>> {
+        match root {
+            None => None,
+            Some(root) => {
+                let left =  Self::invert_tree(
+                    root.borrow_mut().left.take()
+                );
+                let right = Self::invert_tree(
+                    root.borrow_mut().right.take()
+                );
+
+                root.borrow_mut().left = right;
+                root.borrow_mut().right = left;
+
+                Some(root)
+            }
+        }        
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_226() {
+        Solution::invert_tree(tree![2, 1, 3]);
+    }
+}