写的有点乱 哈哈，但是有点简单

#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;


const int N = 1110;

int da[N];
vector<vector<int>> ch(N);

int g[N][N];
vector<int> A;

int n,k;


int main()
{
    cin >> n >> k;
    int max_ = 0;
    int max_index = 0;
    for(int i = 1; i <= k; i++)
    {
        int a,b;
        cin >> a >> b;
        A.push_back(a);
        g[a][b] = 1;
        da[b]++;
        ch[a].push_back(b);
        if(max_ < ch[a].size())
        {
            max_index = a;
            max_ = ch[a].size();
        }

    }
    int root = 1;
    for(int i = 0; i < A.size(); i++)
    {
        if(da[A[i]] == 0)
        {
            root = A[i];
            break;
        }
    }
    cout  << root << endl;
    cout  << max_index << endl;
    sort(ch[max_index].begin(),ch[max_index].end());
    for(int i = 0; i < ch[max_index].size(); i++)
    {
        cout << ch[max_index][i] << " ";
    }
    cout <<endl;

    //找到root
}