递归与二叉树_leetcode404

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None


# 思考误区:当只有根节点时，这个根是不能同时作为子节点的，当时在这一点上，思考不过来

class Solution(object):
    def sumOfLeftLeaves(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """

        if not root:
            return 0

        if root.left and  not root.left.left and not root.left.right:

            return  root.left.val + self.sumOfLeftLeaves(root.right)


        return self.sumOfLeftLeaves(root.left)+self.sumOfLeftLeaves(root.right)