bzoj1179 [Apio2009]抢掠计划atm

http://www.elijahqi.win/archives/966
tarjan缩点 然后spfa即可

#include<cstdio> 
#include<stack>
#include<queue>
#define N 550000
#define M 550000
inline int read(){
    int x=0,f=1;char ch=getchar();
    while (ch<'0'||ch>'9') {if (ch=='-') f=-1;ch=getchar();}
    while (ch<='9'&&ch>='0'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}
struct node{int x,y,next;}data[M],data1[M];
inline int min(int x,int y){return x<y?x:y;}
std::stack<int> q;bool stackf[N],flag[N];
int h1[N],h[N],f[N],size[N],b[N],s,n,m,S,pp,a[N],low[N],dfn[N],num;
void tarjan(int x){
    dfn[x]=++num;low[x]=num;stackf[x]=true;q.push(x);
    for (int i=h[x];i;i=data[i].next){
        int y=data[i].y;
        if (!dfn[y]) tarjan(y),low[x]=min(low[x],low[y]);else if (stackf[y]) low[x]=min(low[x],dfn[y]);
    }
    if (low[x]==dfn[x]){
        ++s;int y;
        do{ y=q.top();
            b[y]=s;q.pop();stackf[y]=false;size[s]+=a[y];
        }while (y!=x);
    }
}
std::queue<int> qq;
void spfa(int xx){
    qq.push(xx);flag[xx]=true;f[xx]=size[xx];
    while (!qq.empty()){
        int x=qq.front();qq.pop();flag[x]=false;
        for (int i=h1[x];i;i=data1[i].next){
            int y=data1[i].y;
            if (f[x]+size[y]>f[y]){
                f[y]=f[x]+size[y];
                if (flag[y]==false){
                    flag[y]=true;qq.push(y);
                }
            }
        }
    }
}
int main(){
    freopen("bzoj1179.in","r",stdin);
    n=read();m=read();
    for (int i=1;i<=m;++i){
        int x=read(),y=read();
        data[++num].y=y;data[num].next=h[x];h[x]=num;
    }num=0;
    for (int i=1;i<=n;++i) a[i]=read();
    for (int i=1;i<=n;++i) if (!dfn[i]) tarjan(i);num=0;//printf("%d ",s);
//  for (int i=1;i<=n;++i) printf("%d ",b[i]);
    for (int i=1;i<=n;++i){
        for (int j=h[i];j;j=data[j].next){
            int y=data[j].y;
            if (b[i]!=b[y]){
                data1[++num].y=b[y];data1[num].next=h1[b[i]];h1[b[i]]=num; data1[num].x=b[i];
                //printf("%d %d\n",b[i],b[y]);
            }
        }
    }
    //for (int i=1;i<=num;++i) printf("%d %d\n",data1[i].x,data1[i].y);
    S=read();pp=read();
    spfa(b[S]);int p,ans=0;
    for (int i=1;i<=pp;++i) p=read(),ans=std::max(ans,f[b[p]]);
    printf("%d",ans);
    return 0;
}