comefrom: <qiyuangong>617_Merge_Two_Binary_Trees_1.py
code: def mergeTrees( t1, t2):
      if t1 is None:
          return t2
      stack = [(t1, t2)]
      while len(stack) != 0:
          n1, n2 = stack.pop()
          if n1 is None or n2 is None:
              continue
          n1.val += n2.val
          if n1.left is None:
              n1.left = n2.left
          else:
              stack.insert(0, (n1.left, n2.left))
          if n1.right is None:
              n1.right = n2.right
          else:
              stack.insert(0, (n1.right, n2.right))
      return t1
masked: def sample_funcname ( var_0 , var_1 ) :
      if var_0 is None :
          return var_1
      var_3 = [ ( var_0 , var_1 ) ]
      while len ( var_3 ) != 0 :
          var_7 , var_8 = var_3.pop ( )
          if var_7 is None or var_8 is None :
              continue
          var_7.val += var_8.val
          if var_7.left is None :
              var_7.left = var_8.left
          else :
              var_3.insert ( 0 , ( var_7.left , var_8.left ) )
          if var_7.right is None :
              var_7.right = var_8.right
          else :
              var_3.insert ( 0 , ( var_7.right , var_8.right ) )
      return var_0
  