BZOJ 1179: [Apio2009]Atm

/**************************************************************
Problem: 1179
User: bblss123
Language: C++
Result: Accepted
Time:5184 ms
Memory:53404 kb
****************************************************************/

#include<iostream>
#include<string.h>
#include<stdio.h>
#include<algorithm>
#include<vector>
#include<stack>
#include<map>
using namespace std;
const int M=5e5+5;
int sccid[M],pre[M],lowlink[M],dfs_clock,allc;
#define ph push
#pragma comment(linker, "/STACK:1024000000,1024000000")
struct Edge{int to,nxt;}edge[M<<1],G[M<<1];
int head[M],work[M],tot,tot_edge;
inline void Add(int from,int to){
edge[tot]=(Edge){to,head[from]};
head[from]=tot++;
}
inline void add_edge(int from,int to){
G[tot_edge]=(Edge){to,work[from]};
work[from]=tot_edge++;
}
stack<int>stk;
int val[M],w[M];
inline void Min(int &a,int b){if(a>b)a=b;}
inline void predfs(int v){
pre[v]=lowlink[v]=++dfs_clock;
stk.ph(v);
for(int i=head[v];~i;i=edge[i].nxt){
int to=edge[i].to;
if(!pre[to])predfs(to),Min(lowlink[v],lowlink[to]);
else if(!sccid[to])Min(lowlink[v],pre[to]);
}
if(pre[v]==lowlink[v]){
sccid[v]=++allc;
for(;!stk.empty();){
int k=stk.top();stk.pop();
sccid[k]=allc;
val[allc]+=w[k];
if(k==v)break;
}
}
}
inline void rd(int &a){
a=0;char c;
while(c=getchar(),!isdigit(c));
do a=a*10+(c^48);
while(c=getchar(),isdigit(c));
}
int n,m,s,p;
map<int,bool>flag[M];
inline void Graph(){
for(int i=1;i<=n;++i){
for(int j=head[i];~j;j=edge[j].nxt){
int to=edge[j].to;
if(sccid[to]==sccid[i])continue;
if(flag[sccid[i]].find(sccid[to])==flag[sccid[i]].end())
add_edge(sccid[i],sccid[to]),flag[sccid[i]][sccid[to]]=1;
}
}
}
inline void Max(int &a,int b){if(a<b)a=b;}
int ans=0,dis[M];
#include<queue>
queue<int>que;
bool ins[M];
inline void spfa(){
memset(dis,0,sizeof(dis));
que.ph(sccid[s]);
dis[sccid[s]]=val[sccid[s]];
for(;!que.empty();){
int v=que.front();que.pop();
for(int i=work[v];~i;i=G[i].nxt){
int to=G[i].to;
if(dis[v]+val[to]>dis[to]){
dis[to]=dis[v]+val[to];
if(!ins[to])ins[to]=1,que.push(to);
}
}
ins[v]=0;
}
}
int main(){
cin>>n>>m;
memset(head,-1,sizeof(head));
memset(work,-1,sizeof(work));
for(int i=1,a,b;i<=m;++i)
rd(a),rd(b),Add(a,b);
for(int i=1;i<=n;++i)rd(w[i]);
cin>>s>>p;
for(int i=1;i<=n;++i)
if(!pre[i])predfs(i);
Graph();
spfa();
for(int a;p--;)rd(a),Max(ans,dis[sccid[a]]);
cout<<ans<<endl;
return 0;
}