101. Symmetric Tree

Author: papilo-cloud

Trees/is_symmetric.py

@@ -0,0 +1,37 @@
+# Given the root of a binary tree, check whether it is a mirror of itself
+# (i.e., symmetric around its center).
+
+
+# Example 1:
+# Input: root = [1,2,2,3,4,4,3]
+# Output: true
+
+# Example 2:
+# Input: root = [1,2,2,null,3,null,3]
+# Output: false
+ 
+
+# Constraints:
+# The number of nodes in the tree is in the range [1, 1000].
+# -100 <= Node.val <= 100
+
+
+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:
+        def symmetric(root1, root2):
+            if (not root1) and (not root2):
+                return True
+            if (not root1) or (not root2):
+                return False
+            if root1.val != root2.val:
+                return False
+            return (symmetric(root1.left, root2.right) and symmetric(root1.right, root2.left))
+
+        return symmetric(root, root)