路径总和 III

from collections import defaultdict
class TreeNode:
    def __init__(____):
        self.val = val
        self.left = left
        self.right = right

def solve():
    def pathSum(____):
        count = ____
        prefix_sum = defaultdict(____)
        prefix_sum[____] = ____
        def dfs(____):
            nonlocal count
            if not node:
                return
            curr_sum += node.val
            count += prefix_sum[curr_sum - targetSum]
            prefix_sum[curr_sum] += ____
            dfs(____)
            dfs(____)
            prefix_sum[curr_sum] -= ____
        dfs(____)
        return count
    root = TreeNode(____, TreeNode(____, TreeNode(____, TreeNode(____), TreeNode(____)), TreeNode(____, None, TreeNode(____))), TreeNode(-____, None, TreeNode(____)))
    print(pathSum(____))