diff --git a/src/problem/mod.rs b/src/problem/mod.rs
index 4d1cc51..ef61b66 100644
--- a/src/problem/mod.rs
+++ b/src/problem/mod.rs
@@ -141,4 +141,5 @@ mod p224_basic_calculator;
 mod p21_merge_two_sorted_lists;
 mod p104_maximum_depth_of_binary_tree;
 mod p100_same_tree;
-mod p226_invert_binary_tree;
\ No newline at end of file
+mod p226_invert_binary_tree;
+mod p101_symmetric_tree;
\ No newline at end of file
diff --git a/src/problem/p101_symmetric_tree.rs b/src/problem/p101_symmetric_tree.rs
new file mode 100644
index 0000000..c2cac57
--- /dev/null
+++ b/src/problem/p101_symmetric_tree.rs
@@ -0,0 +1,71 @@
+/**
+ * [101] Symmetric 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 {
+    fn is_same(left: &Option<Rc<RefCell<TreeNode>>>, right: &Option<Rc<RefCell<TreeNode>>>) -> bool {
+        if left.is_some() ^ right.is_some() {
+            return false;
+        }
+
+        if left.is_none() && right.is_none() {
+            return true;
+        }
+
+        let left = left.as_ref().unwrap();
+        let right = right.as_ref().unwrap();
+
+        if left.borrow().val != right.borrow().val {
+            return false;
+        }
+
+        Self::is_same(&left.borrow().left, &right.borrow().right) 
+            && Self::is_same(&left.borrow().right, &right.borrow().left)
+    }
+
+    pub fn is_symmetric(root: Option<Rc<RefCell<TreeNode>>>) -> bool {
+        if let Some(root) = root {
+            return Self::is_same(&root.borrow().left, &root.borrow().right);
+        }
+
+        true
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_101() {
+        assert!(Solution::is_symmetric(tree![1,2,2,3,4,4,3]));
+        assert!(!Solution::is_symmetric(tree!(1,2,2,"null",3,"null",3)))
+    }
+}