相关疑难解决方法(0)

我正在树上做这个基本的 dp（动态规划）问题（https://cses.fi/problemset/task/1674/）。给定公司的结构（层次结构是一棵树），任务是计算每个员工的下属人数。

这：

import sys
from functools import lru_cache  # noqa
sys.setrecursionlimit(2 * 10 ** 9)

if __name__ == "__main__":
    n: int = 200000
    boss: list[int] = list(range(1, 200001))  
    # so in my example it will be a tree with every parent having one child
    graph: list[list[int]] = [[] for _ in range(n)]

    for i in range(n-1):
        graph[boss[i] - 1].append(i+1)  # directed so neighbours of a node are only its children

    @lru_cache(None)
    def dfs(v: int) -> int:
        if …