【模板】拓扑排序

//https://www.nowcoder.com/practice/88f7e156ca7d43a1a535f619cd3f495c
#include <bits/stdc++.h>
using namespace std;
const int N=2e5+10,M=N;
int n,m;
int head[N],Next[M],to[M],cnt;
int indegree[N],ans[N];
int h,t;
int q[N];
void build(){
    cnt=1;
    h=t=0;
    memset(head,0,sizeof head);
	memset(indegree,0,sizeof indegree);
}
void addEdge(int u,int v){
    Next[cnt]=head[u];
    to[cnt]=v;
    head[u]=cnt++;
}
bool topoSort(){
    for(int i=1;i<=n;i++) if(indegree[i]==0) q[t++]=i;
    int fill=0;
    while(h<t){
        int u=q[h++];
        ans[++fill]=u;
        for(int ei=head[u],v;ei;ei=Next[ei]){
            v=to[ei];
            if(--indegree[v]==0) q[t++]=v;
        }
    }
    return fill==n;
}
int main(){
    scanf("%d%d",&n,&m);
    build();
    for(int i=1,u,v;i<=m;i++){
        scanf("%d%d",&u,&v);
        indegree[v]++;
        addEdge(u,v);
    }
    if(!topoSort()) puts("-1");
    else{
        printf("%d",ans[1]);
        for(int i=2;i<=n;i++) printf(" %d",ans[i]);
    }
    return 0;
}