leetcode112. Path Sum

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.

# Definition for a binary tree node.# class TreeNode(object):#     def __init__(self, x):#         self.val = x#         self.left = None#         self.right = Noneclass Solution(object):    def hasPathSum(self, root, sum):        """        :type root: TreeNode        :type sum: int        :rtype: bool        """        if root==None:            return False        elif root.val==sum and root.left==None and root.right==None:            return True        return self.hasPathSum(root.left,sum-root.val) or self.hasPathSum(root.right,sum-root.val)