万妖穴

拓扑排序

#include<cstdio>
#include<vector>
#include<queue>
#include<algorithm>
using namespace std;
const int maxn=1002;
vector<int>G[maxn];
int Din[maxn]={0};
int n,m;
int ans[maxn];
priority_queue<int,vector<int>,greater<int> >q;
int main(){
    scanf("%d %d",&n,&m);
    for(int i=0;i<m;i++){
        int a,b;
        scanf("%d %d",&a,&b);
        G[a].push_back(b);
        Din[b]++;
    }
    for(int i=0;i<n;i++){
        if(Din[i]==0)q.push(i);
    }
    int cnt=0;
    while(q.size()){
        int x=q.top();
        q.pop();
        ans[cnt]=x;
        cnt++;
        for(int i=0;i<G[x].size();i++){
            Din[G[x][i]]--;
            if(Din[G[x][i]]==0)q.push(G[x][i]);
        }
    }
    if(cnt==n){
        printf("YES\n");
        for(int i=0;i<cnt;i++){
            printf("%d",ans[i]);
            if(i!=cnt-1)printf(" ");
            else printf("\n");
        }
    }else printf("NO\n%d\n",n-cnt);
    return 0;
}