437. Path Sum III (Medium) - TengnanYao/daily_leetcode GitHub Wiki

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution(object):
    def pathSum(self, root, targetSum):
        """
        :type root: TreeNode
        :type targetSum: int
        :rtype: int
        """
        self.result = 0
        def calSum(root, s, cur):
            if root:
                cur += root.val
                if cur == s:
                    self.result += 1
                calSum(root.left, s, cur)
                calSum(root.right, s, cur)
        def dfs(root, s, cur):
            if root:
                calSum(root, s, cur)
                dfs(root.left, s, cur)
                dfs(root.right, s, cur)
        dfs(root, targetSum, 0)
        return self.result