p2805 [NOI2009]植物大战僵尸

传送门

分析

代码

#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<algorithm>
#include<cctype>
#include<cmath>
#include<cstdlib>
#include<queue>
#include<ctime>
#include<vector>
#include<set>
#include<map>
#include<stack>
using namespace std;
#define id(x,y) (x-1)*m+y
const int inf = 1e9+7;
int n,m,s[80000],is[80000],Ans,S,T;
vector<int>p[80000];
vector<int>v[80000];
int dfn[80000],low[80000],ist[80000],cnt,sum,belong[80000],tot[80000];
stack<int>a;
inline void tarjan(int x){
    low[x]=dfn[x]=++cnt;
    a.push(x);
    ist[x]=1;
    for(int i=0;i<v[x].size();i++){
      if(!dfn[v[x][i]]){
          tarjan(v[x][i]);
          low[x]=min(low[x],low[v[x][i]]);
      }else if(ist[v[x][i]]){
          low[x]=min(low[x],dfn[v[x][i]]);
      }
    }
    if(low[x]==dfn[x]){
      sum++;
      while(1){
          int u=a.top();
          a.pop();
          ist[u]=0;
          belong[u]=sum;
          tot[sum]++;
          if(u==x)break;
      }
    }
}
int head[2000100],w[2000100],nxt[2000100],to[2000100],ano[2000100],res;
int level[80000],cur[2000100];
inline void add(int x,int y,int z){
    nxt[++res]=head[x];head[x]=res;to[res]=y;w[res]=z;
    nxt[++res]=head[y];head[y]=res;to[res]=x;w[res]=0;
    ano[res]=res-1;ano[res-1]=res;
}
inline bool bfs(){
    memset(level,-1,sizeof(level));
    queue<int>q;
    level[S]=0;
    q.push(S);
    while(!q.empty()){
      int x=q.front();
      q.pop();
      for(int i=head[x];i;i=nxt[i])
        if(level[to[i]]==-1&&w[i]){
          level[to[i]]=level[x]+1;
          if(to[i]==T)return 1;
          q.push(to[i]);
        }
    }
    return 0;
}
inline int dfs(int x,int flow){
    if(x==T||!flow)return flow;
    int res=0;
    cur[x]=head[x];
    for(int i=cur[x];i;i=nxt[i]){
      cur[x]=i;
      if(level[to[i]]==level[x]+1&&w[i]){
          int f=dfs(to[i],min(flow-res,w[i]));
          w[i]-=f;
          w[ano[i]]+=f;
          res+=f;
      }
    }
    if(!res)level[x]=-1;
    return res;
}
int main(){
    int i,j,k,x;
    scanf("%d%d",&n,&m);
    S=n*m+10,T=S+1;
    for(i=1;i<=n;i++)
      for(j=1;j<=m;j++){
        scanf("%d",&s[id(i,j)]);
          scanf("%d",&x);
          for(k=1;k<=x;k++){
          int y,z;
          scanf("%d%d",&y,&z);
          p[id(i,j)].push_back(id(y+1,z+1)); 
        } 
      }
    for(i=1;i<=n;i++)
      for(j=1;j<=m;j++){
          if(j!=1)v[id(i,j)].push_back(id(i,j-1));
          for(k=0;k<p[id(i,j)].size();k++)
            v[id(i,j)].push_back(p[id(i,j)][k]);
      }
    for(i=1;i<=n*m;i++)
      if(!dfn[i])tarjan(i);
    for(i=1;i<=n;i++)
      for(j=m;j>0;j--)
        if(tot[belong[id(i,j)]]!=1){
          for(k=j;k>0;k--){
            is[id(i,k)]=1;
          }
          break;
        }
    for(i=1;i<=n;i++)
      for(j=1;j<=m;j++){
          if(is[id(i,j)])continue;
          if(j!=1&&!is[id(i,j-1)])add(id(i,j),id(i,j-1),inf);
          for(k=0;k<p[id(i,j)].size();k++)
            if(!is[p[id(i,j)][k]])add(id(i,j),p[id(i,j)][k],inf);
          if(s[id(i,j)]>0){
            Ans+=s[id(i,j)];
            add(id(i,j),T,s[id(i,j)]);
          }else {
            add(S,id(i,j),-s[id(i,j)]);
          }
      }
    while(bfs())while(int a=dfs(S,inf))Ans-=a;
    cout<<Ans;
    return 0;
}