代码如下

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int dfs(vector<vector<int>> &adjacent, int root, vector<int>& memory)
{
    if (memory[root])
    {
        return memory[root];
    }
    else
    {
        int maxn = root;
        for (int neighbor : adjacent[root])
        {
            maxn = max(maxn, dfs(adjacent, neighbor, memory));
        }
        memory[root]=maxn;
        return maxn;
    }
}

int main()
{
    // graph initialization
    int n, m;
    cin >> n >> m;
    vector<vector<int>> adjacent=vector<vector<int>>(n+1);
    int x, y;
    for (int i = 0; i < m; i++)
    {
        cin >> x >> y;
        adjacent[x].push_back(y);
    }

    vector<int> memory=vector<int>(n+1);
    for (int i = 1; i <= n; i++)
    {
        sort(adjacent[i].begin(),adjacent[i].end());
        dfs(adjacent, i, memory);
        cout<<memory[i]<<" ";
    }
}

https://www.luogu.com.cn/record/176195938