BZOJ 4010: [HNOI2015]菜肴制作|拓扑排序贪心

来源：互联网发布：腾讯云主机绑定域名编辑：程序博客网时间：2024/06/06 05:12

找一个反图的拓扑序最大即可
贪心性显然

#include<set>#include<map>#include<ctime>#include<queue>#include<cmath>#include<cstdio>#include<vector>#include<cstring>#include<cstdlib>#include<iostream>#include<algorithm>#define T 111111using namespace std;int sc(){    int i=0,f=1; char c=getchar();    while(c>'9'||c<'0'){if(c=='-')f=-1;c=getchar();}    while(c>='0'&&c<='9')i=i*10+c-'0',c=getchar();    return i*f;}int d[T],head[T],nxt[T],lst[T],ans[T],c[T],b[T],vis[T];int n,m,S,tot,TI;priority_queue<int,vector<int> >q;void Pretreatment(){    tot=0;    for(int i=1;i<=n;i++)        d[i]=head[i]=vis[i]=0;}void insert(int x,int y){    d[y]++;    lst[++tot]=y;    nxt[tot]=head[x];    head[x]=tot;}bool solve(){    int now=n;    while(!q.empty())    {        int x=q.top(); q.pop(); b[now--]=x;        for(int i=head[x];i;i=nxt[i])        {            d[lst[i]]--;            if(!d[lst[i]]) q.push(lst[i]);        }    }    return now==0;}int main(){    S=sc();    while(S--)    {        n=sc(),m=sc();        Pretreatment();        for(int i=1;i<=m;i++)        {            int x=sc(),y=sc();            insert(y,x);        }        for(int i=1;i<=n;i++)if(!d[i])q.push(i);        if(!solve()) puts("Impossible!");        else         {            for(int i=1;i<=n;i++)printf("%d ",b[i]);            puts("");        }    }    return 0;}

0 0