From db6635d09fcb3e8dcfafadb018248519cb15206e Mon Sep 17 00:00:00 2001
From: fartem <jaman.smlnsk@gmail.com>
Date: Sat, 11 Feb 2023 16:04:50 +0300
Subject: [PATCH] 2023-02-11 update: added "100. Same Tree"

---
 README.md                          |  1 +
 lib/easy/symmetric_tree.dart       | 15 +++++++++
 test/easy/symmetric_tree_test.dart | 54 ++++++++++++++++++++++++++++++
 3 files changed, 70 insertions(+)
 create mode 100644 lib/easy/symmetric_tree.dart
 create mode 100644 test/easy/symmetric_tree_test.dart

diff --git a/README.md b/README.md
index f2045be..425a2c8 100644
--- a/README.md
+++ b/README.md
@@ -31,3 +31,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 88. Merge Sorted Array                 | [Link](https://leetcode.com/problems/merge-sorted-array/)                 | [Link](./lib/easy/merge_sorted_array.dart)                 |
 | 94. Binary Tree Inorder Traversal      | [Link](https://leetcode.com/problems/binary-tree-inorder-traversal/)      | [Link](./lib/easy/binary_tree_inorder_traversal.dart)      |
 | 100. Same Tree                         | [Link](https://leetcode.com/problems/same-tree/)                          | [Link](./lib/easy/same_tree.dart)                          |
+| 101. Symmetric Tree                    | [Link](https://leetcode.com/problems/symmetric-tree/)                     | [Link](./lib/easy/symmetric_tree.dart)                     |
diff --git a/lib/easy/symmetric_tree.dart b/lib/easy/symmetric_tree.dart
new file mode 100644
index 0000000..618b234
--- /dev/null
+++ b/lib/easy/symmetric_tree.dart
@@ -0,0 +1,15 @@
+// https://leetcode.com/problems/symmetric-tree/
+import '../common/tree_node.dart';
+
+class Solution {
+  bool isSymmetric(TreeNode? root) {
+    return _isMirror(root?.left, root?.right);
+  }
+
+  bool _isMirror(TreeNode? l, TreeNode? r) {
+    if (l != null && r != null && l.val == r.val) {
+      return _isMirror(l.left, r.right) && _isMirror(l.right, r.left);
+    }
+    return l == null && r == null;
+  }
+}
diff --git a/test/easy/symmetric_tree_test.dart b/test/easy/symmetric_tree_test.dart
new file mode 100644
index 0000000..9fecdf2
--- /dev/null
+++ b/test/easy/symmetric_tree_test.dart
@@ -0,0 +1,54 @@
+import 'package:leetcode_dart/common/tree_node.dart';
+import 'package:leetcode_dart/easy/symmetric_tree.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group(
+    'Example tests',
+    () {
+      final st = Solution();
+      test(
+        'true',
+        () => expect(
+          true,
+          st.isSymmetric(
+            TreeNode(
+              1,
+              TreeNode(
+                2,
+                TreeNode(3),
+                TreeNode(4),
+              ),
+              TreeNode(
+                2,
+                TreeNode(4),
+                TreeNode(3),
+              ),
+            ),
+          ),
+        ),
+      );
+      test(
+        'false',
+        () => expect(
+          false,
+          st.isSymmetric(
+            TreeNode(
+              1,
+              TreeNode(
+                2,
+                null,
+                TreeNode(3),
+              ),
+              TreeNode(
+                2,
+                null,
+                TreeNode(3),
+              ),
+            ),
+          ),
+        ),
+      );
+    },
+  );
+}