101 Symmetric tree

Check the problem description here

Symmetric Tree - LeetCode

Solution

Recursive solution

Recursively check if the mirror nodes are same.

class Solution:
    def isSymmetric(self, root: Optional[TreeNode]) -> bool:
        if root:
            return self.helper(root.left,root.right)
        else:
            return False
    def helper(self,n1,n2):
        if n1==None or n2==None :
            return n1==n2
        if n1.val != n2.val:
            return False
        return (self.helper(n1.left,n2.right) and   self.helper(n1.right,n2.left))

Time :O(N)

Space :O(h) h = height of tree