BZOJ 1565 植物大战僵尸

http://www.lydsy.com/JudgeOnline/problem.php?id=1565

思路:由于植物之间有保护关系:(右边的植物保护左边的植物，植物攻击范围内的植物都被保护了)，因此可以用最大权闭合子图。

 #include<algorithm>
 #include<cstdio>
 #include<cmath>
 #include<cstring>
 #include<iostream>
 #define inf 0x7fffffff
 struct edge{
     int u,v;
 }e[];
 int tot,go[],first[],next[],flow[];
 int op[],cnt[],dis[],n,m,mx[],all,ru[];
 int id[][],w[][],S,T,nodes,pd[],c[];
 int read(){
     int t=,f=;char ch=getchar();
     while (ch<''||ch>'') {if (ch=='-') f=-;ch=getchar();}
     while (''<=ch&&ch<=''){t=t*+ch-'';ch=getchar();}
     return t*f;
 }
 void insert(int x,int y,int z){
     tot++;
     go[tot]=y;
     next[tot]=first[x];
     first[x]=tot;
     flow[tot]=z;
 }
 void add(int x,int y,int z){
     insert(x,y,z);op[tot]=tot+;
     insert(y,x,);op[tot]=tot-;
 }
 int dfs(int x,int f){
     if (x==T) return f;
     int sum=,mn=nodes;
     for (int i=first[x];i;i=next[i]){
         int pur=go[i];
         if (flow[i]&&dis[pur]+==dis[x]){
             int save=dfs(pur,std::min(f-sum,flow[i]));
             sum+=save;
             flow[i]-=save;
             flow[op[i]]+=save;
             if (sum==f||dis[S]>=nodes) return sum;
         }
         if (flow[i]) mn=std::min(mn,dis[pur]);
     }
     if (sum==){
         cnt[dis[x]]--;
         if (cnt[dis[x]]==){
             dis[S]=nodes;
         }else{
             dis[x]=mn+;
             cnt[dis[x]]++;
         }
     }
     return sum;
 }
 int main(){
     n=read();m=read();
     S=;nodes=;
     for (int i=;i<=n;i++)
      for (int j=;j<=m;j++)
       id[i][j]=nodes++;
     for (int i=;i<=n;i++)
      for (int j=;j<=m;j++){
         w[i][j]=read();
         int num=read();
         for (int k=;k<=num;k++){
             int x=read(),y=read();
             x++;y++;
             e[++all].u=id[i][j],e[all].v=id[x][y],ru[e[all].v]++;
         }
     }
     for (int i=;i<=n;i++)
      for (int j=m;j>;j--)
       e[++all].u=id[i][j],e[all].v=id[i][j-],ru[id[i][j-]]++;
     for (int i=;i<=all;i++)
      insert(e[i].u,e[i].v,);
     T=nodes;nodes++;
     int top=;
     for (int i=;i<=nodes-;i++)
      if (ru[i]==)
       pd[i]=,c[++top]=i;
     while (top>){
         int now=c[top--];
         for (int i=first[now];i;i=next[i]){
             int pur=go[i];
             ru[pur]--;
             if (ru[pur]==){
                 pd[pur]=;
                 c[++top]=pur;
             }
         }
     }
     tot=;
     for (int i=;i<=nodes;i++)
       first[i]=;
     for (int i=;i<=all;i++)
      if (pd[e[i].u]&&pd[e[i].v])
       add(e[i].u,e[i].v,inf);
     int sum=;  all=;
     for (int i=;i<=n;i++)
      for (int j=;j<=m;j++)
       if (pd[id[i][j]]){
             if (w[i][j]>) add(id[i][j],T,w[i][j]),sum+=w[i][j];
             else
             if (w[i][j]<) add(S,id[i][j],-w[i][j]);
             all++;
       }
     nodes=all;
     int ans=;
     while (dis[S]<nodes) ans+=dfs(S,inf);
     printf("%d\n",sum-ans);
 }