leetcode

leetcode/101.py

@@ -0,0 +1,38 @@
+# 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 leftSearch(self,stack:List[TreeNode],now:Optional[TreeNode]):
+        if now==None:
+            stack.append(None)
+        else:
+            stack.append(now.val)
+            self.leftSearch(stack,now.left)
+            self.leftSearch(stack,now.right)
+    def rightSearch(self,stack:List[TreeNode],now:Optional[TreeNode]) -> bool:
+        if len(stack)<1:
+            return False
+        if now==None:
+            if not(stack.pop()==now):
+                return False
+            return True
+        elif not self.rightSearch(stack,now.left):
+            return False
+        elif not self.rightSearch(stack,now.right):
+            return False
+        elif not stack.pop()==now.val:
+            return False
+        return True
+
+    def isSymmetric(self, root: Optional[TreeNode]) -> bool:
+        stack=[]
+        self.leftSearch(stack,root.left)
+        isSym=self.rightSearch(stack,root.right)
+
+        if isSym and len(stack)==0:
+            return True
+        else:
+            return False