[APIO2009-C]抢掠计划

Posted 2020-11-15 starve_to_death

题：https://www.cometoj.com/problem/0461

分析：求边双，最后求多汇点最长路

#include<iostream>
#include<cstring>
#include<algorithm>
#include<cstdio>
#include<vector>
#include<queue>
#define pb push_back
using namespace std;
const int M=5e5+5;
int sum[M],book[M],jiu[M],head[M],dfn[M],low[M],vis[M],sta[M],cmp[M],dis[M],val[M],newval[M],tot,top,cnt,num;
vector<int>g[M];
struct node{
    int v,w,nextt;
}e[M];
void tarjan(int u,int f){
    dfn[u]=low[u]=++cnt;
    sta[++top]=u;
    vis[u]=1;
    for(int i=0;i<g[u].size();i++){
        int v=g[u][i];
        if(v==f)
            continue;
        if(!dfn[v]){
            tarjan(v,u);
            low[u]=min(low[u],low[v]);
        }
        else if(vis[v])
            low[u]=min(low[u],dfn[v]);
    }
    if(low[u]==dfn[u]){
        cmp[u]=++tot;
        int countt=val[u];
        vis[u]=0;
        int len=top;
        while(sta[top]!=u){
            countt+=val[sta[top]];
            cmp[sta[top]]=tot;
            vis[sta[top--]]=0;
        }
        top--;
        sum[tot]=len-top;
        newval[tot]=countt;
    }
}
void addedge(int u,int v,int w){
    e[num].v=v;
    e[num].w=w;
    e[num].nextt=head[u];
    head[u]=num++;
}
int spfa(int s,int t){
    for(int i=s;i<=t;i++)
        dis[i]=0,vis[i]=0;
    queue<int>que;
    que.push(s);
    while(!que.empty()){
        int u=que.front();
        que.pop();
        vis[u]=0;
        for(int i=head[u];~i;i=e[i].nextt){
            int v=e[i].v;
            if(dis[v]<dis[u]+e[i].w){
                dis[v]=dis[u]+e[i].w;
                if(!vis[v])
                    vis[v]=1,que.push(v);

            }
        }
    }
    return dis[t];
}
int main(){
    int n,m;
    scanf("%d%d",&n,&m);
    for(int i=0;i<=n;i++)
        head[i]=-1;
    for(int i=1,u,v;i<=m;i++){
        scanf("%d%d",&u,&v);
        g[u].pb(v);
    }
    for(int i=1;i<=n;i++)
        scanf("%d",&val[i]);
    int s,p;
    scanf("%d%d",&s,&p);
    for(int i=1;i<=p;i++)
        scanf("%d",&jiu[i]);
    for(int i=1;i<=n;i++)
        if(!dfn[i])
            tarjan(i,-1);
    s=cmp[s];
    int t=tot+1;
    for(int i=1;i<=n;i++)
        for(int j=0,v;j<g[i].size();j++){
            v=g[i][j];
            if(cmp[i]!=cmp[v]){
    //m            cout<<cmp[i]<<"!!!!!"<<cmp[v]<<"!!!!"<<newval[cmp[i]]<<endl;
                addedge(cmp[i],cmp[v],newval[cmp[i]]);
            }
        }
    for(int i=1;i<=p;i++){
        if(book[cmp[jiu[i]]]==1)
            continue;
        book[cmp[jiu[i]]]=1;
        int w=newval[cmp[jiu[i]]];
    //    if(sum[cmp[jiu[i]]]>1)
    //        w=0;
    //        cout<<cmp[jiu[i]]<<"!!!!!"<<t<<"!!!!"<<w<<endl;
        addedge(cmp[jiu[i]],t,w);
    }
    printf("%d
",spfa(s,t));
}

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