finish 101

leetcode/101.py

@@ -0,0 +1,36 @@
+from typing import Optional
+
+
+# Definition for a binary tree node.
+class TreeNode:
+    def __init__(self, val=0, left=None, right=None):
+        self.val = val
+        self.left = left
+        self.right = right
+
+
+class Solution:
+    def isSymmetric(self, root: Optional[TreeNode]) -> bool:
+        if root is None:
+            return True
+        return self.isMirrorTree(root.left, root.right)
+
+    def isMirrorTree(self, p: Optional[TreeNode], q: Optional[TreeNode]) -> bool:
+        if p is None or q is None:
+            if p is None and q is None:
+                return True
+            return False
+        if p.val != q.val:
+            return False
+        if p.left and q.right:
+            if not self.isMirrorTree(p.left, q.right):
+                return False
+        elif p.left or q.right:
+            return False
+
+        if p.right and q.left:
+            if not self.isMirrorTree(p.right, q.left):
+                return False
+        elif p.right or q.left:
+            return False
+        return True