# Time:  O(n)
# Space: O(h)

# Definition for a binary tree node.
class TreeNode(object):
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None

class Solution(object):
    def flipEquiv(self, root1, root2):
        """
        :type root1: TreeNode
        :type root2: TreeNode
        :rtype: bool
        """
        if not root1 and not root2:
            return True
        if not root1 or not root2 or root1.val != root2.val:
            return False

        return (self.flipEquiv(root1.left, root2.left) and
                self.flipEquiv(root1.right, root2.right) or
                self.flipEquiv(root1.left, root2.right) and
                self.flipEquiv(root1.right, root2.left))