Leetcode 617. Merge Two Binary Trees

import functools
class Solution(object):
    @functools.lru_cache()
    def mergeTrees(self, t1, t2):
        if t1 and t2:
            root = TreeNode(t1.val + t2.val)
            root.left = self.mergeTrees(t1.left, t2.left)
            root.right = self.mergeTrees(t1.right, t2.right)
            return root
        else:
            return t1 or t2