bzoj3232 圈地游戏

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<iostream>
 4 #include<algorithm>
 5 #include<cmath>
 6 #include<queue>
 7 #define N 2550
 8 #define inf 0x7fffffff
 9 #define eps 1e-8
10 using namespace std;
11 int n,m,S,T,a[55][55],b[55][55],c[55][55];
12 double sum;
13 int id(int i,int j){
14     if(!i||!j||i>n||j>m)return T;
15     return (i-1)*m+j;
16 }
17 int e=2,head[N];
18 struct edge{
19     int u,v,next;
20     double f,r;
21 }ed[N<<4];
22 void add(int u,int v,double f){
23     ed[e].u=u;ed[e].v=v;ed[e].f=ed[e].r=f;
24     ed[e].next=head[u];head[u]=e++;
25     ed[e].u=v;ed[e].v=u;ed[e].f=ed[e].r=0;
26     ed[e].next=head[v];head[v]=e++;
27 }
28 int dep[N];
29 bool bfs(){
30     memset(dep,0,sizeof dep);
31     queue<int> Q;
32     Q.push(S);dep[S]=1;
33     while(!Q.empty()){
34         int x=Q.front();Q.pop();
35         for(int i=head[x];i;i=ed[i].next){
36             if(ed[i].f>0&&!dep[ed[i].v]){
37                 dep[ed[i].v]=dep[x]+1;
38                 if(ed[i].v==T)return 1;
39                 Q.push(ed[i].v);
40             }
41         }
42     }
43     return 0;
44 }
45 double dfs(int x,double f){
46     if(x==T||f==0)return f;
47     double ans=0;
48     for(int i=head[x];i;i=ed[i].next){
49         if(ed[i].f>0&&dep[ed[i].v]==dep[x]+1){
50             double nxt=dfs(ed[i].v,min(ed[i].f,f));
51             ans+=nxt;f-=nxt;ed[i].f-=nxt;ed[i^1].f+=nxt;
52         }
53         if(f==0)break;
54     }
55     if(ans==0)dep[x]=-1;
56     return ans;
57 }
58 double dinic(){
59     double ans=0;
60     while(bfs())ans+=dfs(S,inf);
61     return ans;
62 }
63 bool work(double x){
64     for(int i=2;i<e;i++)
65         if(ed[i].u==S)ed[i].f=ed[i].r;
66         else ed[i].f=x*ed[i].r;
67     double ans=dinic();
68     return sum-ans>0;
69 }
70 int main(){
71     scanf("%d%d",&n,&m);
72     S=n*m+1;T=S+1;
73     for(int i=1;i<=n;i++)
74         for(int j=1;j<=m;j++)scanf("%d",&a[i][j]),sum+=a[i][j];
75     for(int i=1;i<=n+1;i++)
76         for(int j=1;j<=m;j++)scanf("%d",&b[i][j]);
77     for(int i=1;i<=n;i++)
78         for(int j=1;j<=m+1;j++)scanf("%d",&c[i][j]);
79     for(int i=1;i<=n;i++){
80         for(int j=1;j<=m;j++){
81             add(S,id(i,j),a[i][j]);
82             add(id(i,j),id(i-1,j),b[i][j]);
83             add(id(i,j),id(i,j-1),c[i][j]);
84             add(id(i,j),id(i+1,j),b[i+1][j]);
85             add(id(i,j),id(i,j+1),c[i][j+1]);
86         }
87     }
88     double l=0,r=1255,mid,ans;
89     while(r-l>eps){
90         mid=(l+r)/2.0;
91         if(work(mid))l=ans=mid;
92         else r=mid;
93     }
94     printf("%0.3lf\n",ans);
95     return 0;
96 }