new_contents: """Leetcode 617. Merge Two Binary Trees
  Easy
  
  URL: https://leetcode.com/problems/merge-two-binary-trees/
  
  Given two binary trees and imagine that when you put one of them to cover the other,
  some nodes of the two trees are overlapped while the others are not.
  
  You need to merge them into a new binary tree. The merge rule is that if two nodes
  overlap, then sum node values up as the new value of the merged node. Otherwise,
  the NOT null node will be used as the node of new tree.
  
  Example 1:
  Input: 
      Tree 1                     Tree 2                  
            1                         2                             
           / \                       / \                            
          3   2                     1   3                        
         /                           \   \                      
        5                             4   7                  
  Output:
  Merged tree:
           3
          / \
         4   5
        / \   \ 
       5   4   7
  
  Note: The merging process must start from the root nodes of both trees.
  """
  
  # Definition for a binary tree node.
  class TreeNode(object):
      def __init__(self, val):
          self.val = val
          self.left = None
          self.right = None
  
  
  class Solution(object):
      def mergeTrees(self, t1, t2):
          """
          :type t1: TreeNode
          :type t2: TreeNode
          :rtype: TreeNode
          """
          pass
  
  
  def main():
      pass
  
  
  if __name__ == '__main__':
      main()
  
subject: Add lc0617_merge_two_binary_trees.py