题目描述

blablabla

样例

blablabla

C++ 代码

#include<iostream>
#include<cstring>
#include<algorithm>
using namespace std;
const int N = 1e5 + 10;
int idx,ne[N],h[N],e[N];
int n,m;
int path[N];
int st[N];
void add(int a,int b)
{
    ne[idx] = h[a],e[idx] = b,h[a] = idx++;
}
bool  topsort()
{
    int tt = 0,hh = -1;
    for(int i = 1; i <= n ;i ++  )
     if(!st[i])
      path[++hh] = i;

    while(tt<=hh)
    {
        int t = path[tt++];
        for(int i = h[t]; i!=-1; i =ne[i])
        {
            int j = e[i];
            if(--st[j]==0) path[++hh] = j;
        }
    }

    return hh == n-1;
}

int main()
{
    cin >> n >> m;
    memset(h,-1,sizeof h);
    for(int i = 0; i < m; i ++ )
    {
        int a,b;
        cin >> a >> b;
        add(a,b);
        st[b]++;
    }
    if(topsort())
       for(int i = 0; i < n; i ++ ) 
         cout << path[i] << " ";
    else cout << -1 << endl;
    return 0;
}