最大流(Isap模板)

http://acm.hdu.edu.cn/showproblem.php?pid=1532

  1 #include <iostream>
  2 #include <cstdio>
  3 #include <climits>
  4 #include <cstring>
  5 #include <algorithm>
  6 using namespace std;
  7 typedef  struct {int v,next,val;} edge;
  8 const int MAXN=20010;
  9 const int MAXM=500010;
 10 edge e[MAXM];
 11 int p[MAXN],eid;
 12 inline void init(){memset(p,-1,sizeof(p));eid=0;}
 13 //有向
 14 inline void insert1(int from,int to,int val)
 15 {
 16     e[eid].v=to;e[eid].val=val;
 17     e[eid].next=p[from];
 18     p[from]=eid++;
 19     swap(from,to);
 20     e[eid].v=to;e[eid].val=0;
 21     e[eid].next=p[from];
 22     p[from]=eid++;
 23 }
 24 //无向
 25 inline void insert2(int from,int to,int val)
 26 {
 27     e[eid].v=to;e[eid].val=val;
 28     e[eid].next=p[from];
 29     p[from]=eid++;
 30     swap(from,to);
 31     e[eid].v=to;e[eid].val=val;
 32     e[eid].next=p[from];
 33     p[from]=eid++;
 34 }
 35 int n,m;//n为点数 m为边数
 36 int h[MAXN];
 37 int gap[MAXN];
 38 int source,sink;
 39 inline int dfs(int pos,int cost)
 40 {
 41     if (pos==sink) return cost;
 42 
 43     int j,minh=n-1,lv=cost,d;
 44     for (j=p[pos];j!=-1;j=e[j].next)
 45     {
 46         int v=e[j].v,val=e[j].val;
 47         if(val>0)
 48         {
 49             if (h[v]+1==h[pos])
 50             {
 51                 if (lv<e[j].val) d=lv;
 52                 else d=e[j].val;
 53 
 54                 d=dfs(v,d);
 55                 e[j].val-=d;
 56                 e[j^1].val+=d;
 57                 lv-=d;
 58                 if (h[source]>=n) return cost-lv;
 59                 if (lv==0) break;
 60             }
 61             if (h[v]<minh)    minh=h[v];
 62         }
 63     }
 64     if (lv==cost)
 65     {
 66         --gap[h[pos]];
 67         if (gap[h[pos]]==0) h[source]=n;
 68         h[pos]=minh+1;
 69         ++gap[h[pos]];
 70     }
 71     return cost-lv;
 72 }
 73 
 74 int isap(int st,int ed)
 75 {
 76 
 77     source=st;sink=ed;
 78     int ret=0;
 79     memset(gap,0,sizeof(gap));
 80     memset(h,0,sizeof(h));
 81     gap[st]=n;
 82     while (h[st]<n)
 83     {
 84         ret+=dfs(st,INT_MAX);
 85     }
 86     return ret;
 87 }
 88 int main()
 89 {
 90     while(cin>>m>>n)
 91     {
 92         init();
 93         for(int i=0;i<m;i++)
 94         {
 95             int u,v,c;
 96             scanf("%d%d%d",&u,&v,&c);
 97             insert1(u,v,c);
 98         }
 99         printf("%d\n",isap(1,n));
100     }
101     return 0;
102 }

 

posted @ 2012-07-20 16:53  qijinbiao1  阅读(1216)  评论(2)    收藏  举报