human
What is a Python program to find all path that the sum of nodes equal to target, the path could be start and end at any node in the tree given the following:
I am working on the file "03_BinaryTree_DivideConquer.ipynb".
The first task is:
Binary Tree Path Sum III

Give a binary tree, and a target number, find all path that the sum of nodes equal to target, the path could be start and end at any node in the tree.
http://www.lintcode.com/en/problem/binary-tree-path-sum-iii/
Validate Binary Search Tree
https://leetcode.com/problems/validate-binary-search-tree/#/description
https://www.lintcode.com/en/problem/validate-binary-search-tree/#
Can you write Python program for it?
assistant
#Here is Python program to find all path that the sum of nodes equal to target, the path could be start and end at any node in the tree.

## brilliant solver!!

"""
Definition of TreeNode:
class TreeNode:
    def __init__(self, val):
        self.val = val
        self.left, self.right = None, None
"""
class Solution:
    """
    @param root: The root of binary tree.
    @return: True if the binary tree is BST, or false
    """  
    def isValidBST(self, root):
        # write your code here
        return self.helper(root, -0x80000000-1, 0x7FFFFFFF+1)
        
    def helper(self, root, min, max):
        if root is None:
            return True
        elif root.val <= min or root.val >= max:
            return False
        else:
            return self.helper(root.left, min, root.val) \
            and self.helper(root.right, root.val, max)