Question
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
Follow up: Could you solve it both recursively and iteratively?
Python Solution
def rec(ln,rn):
if ln==None and rn==None:
return True
elif ln==None or rn==None:
return False
if ln.val!=rn.val:
return False
l = rec(ln.left,rn.right)
r = rec(ln.right,rn.left)
return l and r
class Solution:
def isSymmetric(self, root: TreeNode) -> bool:
if not root:
return True
return rec(root.left,root.right)
