hdu 3046 Pleasant sheep and big big wolf 最小割

  1 #include<iostream>
  2 #include<cstdio>
  3 #include<cstring>
  4 #include<cstdlib>
  5 #include<cmath>
  6 #include<algorithm>
  7 #include<queue>
  8 #define inf 0x7fffffff
  9 using namespace std;
 10 const int maxn=200*200+10;
 11 int n,m;
 12 struct node
 13 {
 14     int u,flow;
 15     int next;
 16 }edge[maxn*4];
 17 int head[maxn],edgenum;
 18 int from,to;
 19 
 20 void add(int u,int v,int flow)
 21 {
 22     edge[edgenum].u=v ;edge[edgenum].flow=flow;
 23     edge[edgenum].next=head[u];
 24     head[u]=edgenum++;
 25 
 26     edge[edgenum].u=u ;edge[edgenum].flow=0;
 27     edge[edgenum].next=head[v];
 28     head[v]=edgenum++;
 29 }
 30 
 31 int d[maxn];
 32 int bfs()
 33 {
 34     memset(d,0,sizeof(d));
 35     d[from]=1;
 36     queue<int> Q;
 37     Q.push(from);
 38     while (!Q.empty())
 39     {
 40         int u=Q.front() ;Q.pop() ;
 41         for (int i=head[u] ;i!=-1 ;i=edge[i].next)
 42         {
 43             int v=edge[i].u;
 44             if (!d[v] && edge[i].flow>0)
 45             {
 46                 d[v]=d[u]+1;
 47                 Q.push(v);
 48                 if (v==to) return 1;
 49             }
 50         }
 51     }
 52     return 0;
 53 }
 54 
 55 int dfs(int u,int flow)
 56 {
 57     if (u==to || flow==0) return flow;
 58     int cap=flow;
 59     for (int i=head[u] ;i!=-1 ;i=edge[i].next)
 60     {
 61         int v=edge[i].u;
 62         if (d[v]==d[u]+1 && edge[i].flow>0)
 63         {
 64             int x=dfs(v,min(cap,edge[i].flow));
 65             cap -= x;
 66             edge[i].flow -= x;
 67             edge[i^1].flow += x;
 68             if (cap==0) return flow;
 69         }
 70     }
 71     return flow-cap;
 72 }
 73 int dinic()
 74 {
 75     int sum=0;
 76     while (bfs()) sum += dfs(from,inf);
 77     return sum;
 78 }
 79 int main()
 80 {
 81     int ncase=1;
 82     while (scanf("%d%d",&n,&m)!=EOF)
 83     {
 84         memset(head,-1,sizeof(head));
 85         edgenum=0;
 86         from=n*m+1;
 87         to=from+1;
 88         int a;
 89         for (int i=1 ;i<=n ;i++)
 90         {
 91             for (int j=1 ;j<=m ;j++)
 92             {
 93                 scanf("%d",&a);
 94                 if (a==1)
 95                 {
 96                     add(from,(i-1)*m+j,inf);
 97                 }
 98                 else if (a==2)
 99                 {
100                     add((i-1)*m+j,to,inf);
101                 }
102                 if (i-1>=1) add((i-1)*m+j,(i-2)*m+j,1);
103                 if (i+1<=n) add((i-1)*m+j,i*m+j,1);
104                 if (j-1>=1) add((i-1)*m+j,(i-1)*m+j-1,1);
105                 if (j+1<=m) add((i-1)*m+j,(i-1)*m+j+1,1);
106             }
107         }
108         printf("Case %d:\n%d\n",ncase++,dinic());
109     }
110     return 0;
111 }