# Definition for a  binary tree node# class TreeNode:#     def __init__(self, x):#         self.val = x#         self.left = None#         self.right = Noneclass Solution:    # @param root, a tree node    # @param sum, an integer    # @return a boolean    def hasPathSum(self, root, sum):        ret = False        if root == None:            return ret        sum -= root.val        if sum==0 and root.left==None and root.right==None:            ret = True        return ret or self.hasPathSum(root.left,sum) or self.hasPathSum(root.right,sum)