leetcode——437. 路径总和 III

class Solution:
    def pathSum(self, root: TreeNode, sum: int) -> int:
        if not root:
            return 0
        def dfs(node,sums):
            left=right=0
            temp=[num+node.val for num in sums] + [node.val]
            if node.left:
                left=dfs(node.left,temp)
            if node.right:
                right=dfs(node.right,temp)
            return temp.count(sum)+left+right
        return dfs(root,[])