拓扑排序

#include<bits/stdc++.h>
using namespace std;
#define rep(i,j,k) for(int i=(int)j;i<=(int)k;i++)
#define per(i,j,k) for(int i=(int)k;i>=(int)j;i--)
#define pb push_back
#define pf push_front
#define fi first
#define se second 11
typedef long long ll;
typedef unsigned long long ull;
typedef long double ldb;
typedef double db;
const db PI=acos(-1.0);
const ll INF=0x3f3f3f3f3f3f3f3fLL;
const int inf=0x3f3f3f3f;//0x7fffffff;
const double eps=1e-9;
const ll MOD=9999991;
const int maxn=1e3+5;
vector<int>e[maxn];
int in[maxn];
int n,m;
void solve(){
    priority_queue<int,vector<int>,greater<int> >Q;
    vector<int>ans;
    for(int i=1;i<=n;i++){
    if(in[i]==0)Q.push(i);
    }
    while(!Q.empty()){
    int t=Q.top();Q.pop();
    ans.pb(t);
    for(int i=0;i<e[t].size();i++){
    int y=e[t][i];
    in[y]--;
    if(in[y]==0)Q.push(y);
    }
    
    }
    int len=ans.size();
    // cout<<len<<endl;
    for(int i=0;i<len-1;i++)
    printf("%d ",ans[i]);
    printf("%d\n",ans[len-1]);
}
int main(){
    while(cin>>n>>m){
    for(int i=1;i<=n;i++)e[i].clear();
    rep(i,1,n)in[i]=0;
    while(m--){
    int a,b;
    scanf("%d %d",&a,&b);
    e[a].pb(b);
    in[b]++;
    }
    solve();
    }
    // system("pause");
    return 0;
}