对每个节点递归求和它后面的所有节点

class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next

def recursiveSum(node):
    if node is None:
        return 0
    else:
        return node.val + recursiveSum(node.next)

# 示例用法
# 创建链表：1 -> 2 -> 3 -> 4 -> 5
node5 = ListNode(5)
node4 = ListNode(4, node5)
node3 = ListNode(3, node4)
node2 = ListNode(2, node3)
node1 = ListNode(1, node2)

# 调用递归函数求和
result = recursiveSum(node1)
print(result)  # 输出：15