http://acm.hdu.edu.cn/showproblem.php?pid=4857

题解：逆向拓扑排序

/*
*@Author:   STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
#define endl "\n"
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=30000+10;
const int M=100000+10;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t,n,m,k,p,l,r,u,v;
int ans[N],cnt,flag,temp,sum;
int in[N];
vector<int> G[N];
void dfs(){
    priority_queue<int,vector<int>,less<int> >q;
    for(int i=1;i<=n;i++)
        if(in[i]==0)
            q.push(i);
    while(!q.empty()){
        int tmp=q.top();
        q.pop();
        ans[++cnt]=tmp;
        for(int i=0,j=G[tmp].size();i<j;i++){
            int v=G[tmp][i];
            in[v]--;
            if(in[v]==0){
                q.push(v);
            }
        }
    }
}
void init(){
    memset(in,0,sizeof(in));
    for(int i=1;i<=n;i++)
        G[i].clear();
    cnt=0;
}
int main()
{
#ifdef DEBUG
	freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
#endif
    //ios::sync_with_stdio(false);
    //cin.tie(0);
    //cout.tie(0);
    scanf("%d",&t);
    while(t--){
        scanf("%d%d",&n,&m);
        init();
        for(int i=1;i<=m;i++){
            scanf("%d%d",&u,&v);
            G[v].push_back(u);
            in[u]++;
        }
        dfs();
        for(int i=n;i>=1;i--)
            printf("%d%c",ans[i]," \n"[i==1]);
    }

#ifdef DEBUG
	printf("Time cost : %lf s\n",(double)clock()/CLOCKS_PER_SEC);
#endif
    //cout << "Hello world!" << endl;
    return 0;
}