404. Sum of Left Leaves

class Solution(object):
    def sumOfLeftLeaves(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        left=[]
        if not root:
            return
        
            
        self.sumOfLeftLeaves(root.left)
        left.append(root.val)
        self.sumOfLeftLeaves(root.right)
        
        return sum(left)

class Solution:
    def sumOfLeftLeaves(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        result = 0
        if not root:
            return 0      
        if root.left and not root.left.left and not root.left.right:
            result += root.left.val
        return result+self.sumOfLeftLeaves(root.left)+self.sumOfLeftLeaves(root.right)