leetcode_473.py

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

class Solution(object):
    paths = list()
    path = list()
    def getAllpath(self, root, sum1):
        if not root:
            return
        if sum(self.path) + root.val == sum1:
            self.paths.append(self.path + [root.val])
        self.path.append(root.val)
        self.getAllpath(root.left, sum1)
        self.getAllpath(root.right, sum1)
        self.path.pop(-1)

    def fromRoot(self, root, sum):
        if root is None:
            return
        self.getAllpath(root, sum)
        self.path = list()
        self.fromRoot(root.left, sum)
        self.fromRoot(root.right, sum)

    def pathSum(self, root, sum):
        """
        :type root: TreeNode
        :type sum: int
        :rtype: int
        """
        if root is None:
            return 0
        self.fromRoot(root, sum)
        return len(self.paths)