HDU 4289 Control (最大流+拆点)

  1 /*Dinic算法求最大流*/
  2 #include<stdio.h>
  3 #include<string.h>
  4 #include<iostream>
  5 #define point_MAX 10000
  6 #define edge_MAX 100000
  7 #define INF_MAX 999999999
  8 using namespace std;
  9 struct EDGE
 10 {
 11     int to;/*指向的点*/
 12     int next;/*指向的下一条邻边*/
 13     int w;/*权值*/
 14 }edge[edge_MAX];
 15 int len;/*边的数量*/
 16 int point[point_MAX];
 17 int Vertex,Edge;
 18 int d[point_MAX];
 19 void init()/*初始化*/
 20 {
 21     len=0;
 22     memset(point,0,sizeof(point));
 23 }
 24 int add_edge(int a,int b,int w)/*添加由a指向b的权值为w的边*/
 25 {
 26     len++;
 27     edge[len].w=w;
 28     edge[len].to=b;
 29     edge[len].next=point[a];
 30     point[a]=len;
 31     return 0;/*无重边，插入*/
 32 }
 33 int bfs(int s)
 34 {
 35     int q[point_MAX],front=0,rear=1,j,t,i;
 36     q[0]=s;
 37     memset(d,-1,sizeof(d));/**/
 38     d[s]=0;
 39     while(front<rear)
 40     {
 41        t=q[front++];
 42          for(j=point[t];j;j=edge[j].next)
 43          {
 44             if(d[edge[j].to]==-1&&edge[j].w>0)
 45             {
 46              d[edge[j].to]=d[t]+1;
 47            q[rear++]=edge[j].to;/*逐层增加*/
 48         }
 49          }
 50     }
 51     if(d[Vertex]>=0)
 52        return 1;
 53     return 0;
 54 }
 55 long long min(long long a,long long b)
 56 {
 57     return a<b?a:b;
 58 }
 59 long long dinic(int t,long long sum)/*寻找增广路*/
 60 {
 61     int i,os,j;
 62     long long a;
 63     if(t==Vertex)/*如果已经找到汇点，返回sum*/
 64       return sum;
 65     os=sum;
 66     for(i=point[t];i&&sum;i=edge[i].next)
 67     {
 68        if(d[edge[i].to]==d[t]+1&&edge[i].w>0)/*可行流，即增广路*/
 69        {
 70            a=dinic(edge[i].to,min(sum,edge[i].w));
 71            edge[i].w-=a;
 72            for(j=point[edge[i].to];edge[j].to!=t;j=edge[j].next);
 73            edge[j].w+=a;/*处理反向边*/
 74            sum-=a;
 75        }
 76     }
 77     return os-sum;
 78 }
 79 long long DINIC(int s)/*DINIC算法*/
 80 {
 81      long long ans=0;
 82      while(bfs(s))/*遍历整个图，判断是否已经完成最大流*/
 83        ans+=dinic(s,INF_MAX);/*添加所能增加的流量*/
 84      return ans;
 85 }
 86 
 87 int main()
 88 {
 89      int i,j,x,y,w,S,D;
 90      int cost[205];
 91      while(scanf("%d%d",&Vertex,&Edge)!=EOF)
 92      {
 93         init();
 94         memset(cost,0,sizeof(cost));
 95         scanf("%d%d",&S,&D);
 96         for(i=1;i<=Vertex;i++)
 97         {
 98             scanf("%d",&cost[i]);
 99             add_edge(i,i+Vertex,cost[i]);
100             add_edge(i+Vertex,i,0);
101         }
102         for(i=0;i<Edge;i++)
103         {
104            scanf("%d%d",&x,&y);
105            add_edge(x+Vertex,y,INF_MAX);
106            add_edge(y,x+Vertex,0);
107            add_edge(y+Vertex,x,INF_MAX);/*添加反向边*/
108            add_edge(x,y+Vertex,0);
109         }
110         Vertex=D+Vertex;
111         //cout<<"=="<<endl;
112         printf("%lld\n",DINIC(S));/*以S为源点，Vertex为汇点*/
113      }
114      return 0;
115 }