【Leetcode刷题】：Python：437. 路径总和 III_leetcode437 python

题目

437. 路径总和 III

代码：dfs

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def pathSum(self, root: TreeNode, targetSum: int) -> int:
        self.ans = 0 
        if not root:
            return 0
        def dfs(r, t):
            if not r:
                return
            if r.val == t:
                self.ans += 1
            if r.left:
                dfs(r.left, t-r.val)
            if r.right:
                dfs(r.right, t-r.val)
            return 
        dfs(root, targetSum) 
        self.ans += self.pathSum(root.left, targetSum)
        self.ans += self.pathSum(root.right, targetSum)
        return self.ans
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