new_contents: """Leetcode 404. Sum of Left Leaves
  Easy
  
  URL: https://leetcode.com/problems/sum-of-left-leaves/
  
  Find the sum of all left leaves in a given binary tree.
  
  Example:
      3
     / \
    9  20
      /  \
     15   7
  
  There are two left leaves in the binary tree, with values 9 and 15 respectively. 
  Return 24.
  """
  
  # 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 sumOfLeftLeaves(self, root):
          """
          :type root: TreeNode
          :rtype: int
          """
          pass
  
  
  def main():
      pass
  
  
  if __name__ == '__main__':
      main()
  
subject: Add lc0404_sum_of_left_leaves.py