617. Merge Two Binary Trees.py

# # Definition for a binary tree node.
# # class TreeNode(object):
# #     def __init__(self, val=0, left=None, right=None):
# #         self.val = val
# #         self.left = left
# #         self.right = right
class Solution(object):
    def mergeTrees(self, t1, t2):
        if t1 == None:
            return t2

        if t2 == None:
            return t1

        t1.val = t1.val + t2.val
        t1.left = self.mergeTrees(t1.left, t2.left)
        t1.right = self.mergeTrees(t1.right, t2.right)

        return t1