bzoj 1179（tarjan缩点+最长路）

传送门
用tarjan缩点后在DAG上跑一个SPFA最长路即可，数组有点多，该赋初值一定要赋初值。

#include
#include
#include
#include
#include
#include
#include
using namespace std;
const int maxn=500002;
int head[maxn],edge=0,n,m,source,P;
int val[maxn];
int pub[maxn],dfn[maxn],low[maxn],ins[maxn],belong[maxn];
int alc[maxn],sum[maxn],dis[maxn],scc=0,cnt=0;
struct EDGE {
    int u,v,nxt;
}e[maxn];
stack<int> S;
vector<int> G[maxn];
inline int read() {
    int x=0;char c=getchar();
    while (c<'0'||c>'9') c=getchar();
    while (c>='0'&&c<='9') x=x*10+c-'0',c=getchar();
    return x;
}
inline void adde(int u,int v) {
    e[edge].nxt=head[u],e[edge].u=u,e[edge].v=v,head[u]=edge++;
}
void dfs(int p) {   
    dfn[p]=low[p]=++cnt;
    ins[p]=1;
    S.push(p);
    for (int i=head[p];~i;i=e[i].nxt) {
        int v=e[i].v;
        if (!dfn[v]) {
            dfs(v);
            low[p]=min(low[p],low[v]);
        }
        else if (ins[v])
            low[p]=min(low[p],dfn[v]);
    }
    if (low[p]==dfn[p]) {
        sum[++scc]=alc[scc]=0;
        while (!S.empty()) {
            int t=S.top();
            S.pop();
            ins[t]=0,belong[t]=scc,sum[scc]+=val[t];
            if (t==source) source=scc;
            if (pub[t]) alc[scc]=1;
            if (t==p) break;
        }
    }
}
void tarjan() {
    for (register int i=1;i<=n;++i)
        if (!dfn[i]) dfs(i);
    for (register int i=0;iint u=belong[e[i].u],v=belong[e[i].v];
        if (u!=v) G[u].push_back(v);
    }
}
inline void spfa(int source) {
    queue<int> q;
    bool inq[maxn];
    memset(inq,false,sizeof(inq));
    memset(dis,-1,sizeof(dis));
    inq[source]=1,dis[source]=sum[source];
    q.push(source);
    while (!q.empty()) {
        int p=q.front(),siz=G[p].size();
        q.pop(),inq[p]=false;
        for (int j=0;jint v=G[p][j];
            if (dis[v]if (!inq[v]) {
                    inq[v]=true;
                    q.push(v);
                }
            }
        }
    }
    int ans=0;
    for (int i=1;i<=scc;++i)
        if (alc[i]) ans=max(ans,dis[i]);
    printf("%d\n",ans);
}
int main() {
//  freopen("bzoj 1179.in","r",stdin);
    memset(head,-1,sizeof(head));
    n=read(),m=read();
    while (m--) {
        int u,v;
        u=read(),v=read();
        adde(u,v);
    }
    for (register int i=1;i<=n;++i) val[i]=read(),G[i].clear(),dfn[i]=pub[i]=0;
    source=read(),P=read();
    while (P--) pub[read()]=1;
    tarjan();
    spfa(source);
//  for (int i=1;i<=scc;++i) printf("%d:%d\n",i,sum[i]);
//  for (register int i=1;i<=n;++i) printf("%d:%d\n",i,belong[i]);
    return 0;
}