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<cstdio>#include<cstring>#include<iostream>#include<algorithm>#include<stack>#include<queue>#include<vector>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;i<edge;++i) {        int 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;j<siz;++j) {            int v=G[p][j];            if (dis[v]<dis[p]+sum[v]) {                dis[v]=dis[p]+sum[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;}