113. 路径总和 II

给你二叉树的根节点 root 和一个整数目标和 targetSum，找出所有 从根节点到叶子节点路径总和等于给定目标和的路径。

叶子节点是指没有子节点的节点。

示例 1：

输入：root = [5,4,8,11,null,13,4,7,2,null,null,5,1], targetSum = 22
输出：[[5,4,11,2],[5,8,4,5]]

示例 2：

输入：root = [1,2,3], targetSum = 5
输出：[]

示例 3：

输入：root = [1,2], targetSum = 0
输出：****[]

提示：

• 树中节点总数在范围 [0, 5000] 内
• -1000 <= Node.val <= 1000
• -1000 <= targetSum <= 1000

Python 解答：

# 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) -> List[List[int]]:
        res = []
        def dfs(root, temp, target):
            # if not root and not target:
            #     return 
            # elif not root and target:
            #     return
            if not root:
                return
            elif root and not root.left and not root.right and root.val == target:
                res.append(temp+[root.val])
            else:
                dfs(root.left, temp+[root.val], target-root.val)
                dfs(root.right, temp+[root.val], target-root.val)
        dfs(root, [], targetSum)
        return res