Welcome Party ZOJ - 4109

​​http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemCode=4109​​

不开心总人数即连通块数 每个块出一个编号最小的人 贪心考虑 与其相识的人可以下批入场 优先队列维护拓扑即可

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>
#include <queue>
#define pb push_back
using namespace std;
typedef long long ll;
const int maxn=1e6+10;

struct node
{
    int val;
    bool friend operator < (node n1,node n2){
        return n1.val>n2.val;
    }
};

vector <int> edge[maxn];
priority_queue <node> que;
int f[maxn],minn[maxn],ans[maxn],book[maxn];
int n,m,num,tot;

void init()
{
    int i;
    for(i=1;i<=n;i++){
        edge[i].clear();
        f[i]=i,minn[i]=i,book[i]=0;
    }
}

int getf(int p)
{
    if(f[p]==p) return p;
    else return f[p]=getf(f[p]);
}

void unite(int u,int v)
{
    int fu,fv;
    fu=getf(u),fv=getf(v);
    if(fu!=fv){
        f[fv]=fu;
        minn[fu]=min(minn[fu],minn[fv]);
    }
}

void toposort()
{
    node cur,tmp;
    int i,u,v;
    while(!que.empty()) que.pop();
    num=0,tot=0;
    for(i=1;i<=n;i++){
        if(f[i]==i){
            tmp.val=minn[i];
            que.push(tmp);
            book[minn[i]]=1;
            tot++;
        }
    }
    while(!que.empty()){
        cur=que.top();
        que.pop();
        u=cur.val;
        ans[++num]=u;
        for(i=0;i<edge[u].size();i++){
            v=edge[u][i];
            if(!book[v]){
                tmp.val=v;
                que.push(tmp);
                book[v]=1;
            }
        }
    }
}

int main()
{
    int t,i,u,v;
    scanf("%d",&t);
    while(t--){
        scanf("%d%d",&n,&m);
        init();
        while(m--){
            scanf("%d%d",&u,&v);
            edge[u].pb(v),edge[v].pb(u);
            unite(u,v);
        }
        toposort();
        printf("%d\n",tot);
        for(i=1;i<=n;i++){
            printf("%d",ans[i]);
            if(i<n) printf(" ");
            else printf("\n");
        }
    }
    return 0;
}