Merge pull request gzc426#304 from Scottnan/master

gzc426 · web-flow · commit 765ea1c39d0d · 2018-12-04T17:21:31.000+08:00
Create Despacito.md
diff --git a/2018.12.04-leetcode101/Despacito.md b/2018.12.04-leetcode101/Despacito.md
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+# leetcode 101 Symmetric Tree
+## 1. Description
+Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).
+
+For example, this binary tree [1,2,2,3,4,4,3] is symmetric:
+
+                  1
+                 / \
+                2   2
+               / \ / \
+              3  4 4  3
+
+But the following [1,2,2,null,3,null,3] is not:
+
+                  1
+                 / \
+                2   2
+                 \   \
+                 3    3
+
+**Note:**
+
+Bonus points if you could solve it both recursively and iteratively.
+
+## 2. Solution
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution:
+    def isSymmetric(self, root):
+        """
+        :type root: TreeNode
+        :rtype: bool
+        """
+        if root == None:
+            return True
+        return self.comroot(root.left, root.right)
+    
+    def comroot(self, left, right):
+        if left == None and right == None:
+            return True
+        elif left == None or right == None:
+            return False
+        elif left.val != right.val:
+            return False
+        return self.comroot(left.left, right.right) and self.comroot(left.right, right.left)
+```
