【最大流Dinic模板】HDU1532&POJ1273-Drainage Ditches（16/3/6更正）

 #include<iostream>
 #include<cstdio>
 #include<cstdlib>
 #include<cstring>
 #include<algorithm>
 #include<cmath>
 #include<vector>
 using namespace std;
 const int MAXN=;
 const int INF=0x7fffffff;
 int n,m;//n:edges,m:points
 struct node
 {
        int to,pos,cap;
 };
 vector<node> E[MAXN];
 int vis[MAXN];

 void addedge(int u,int v,int w)
 {
      node x;
      x.to=v; x.pos=E[v].size(); x.cap=w;
      E[u].push_back(x);
      x.to=u; x.pos=E[u].size()-; x.cap=;
      E[v].push_back(x);
 }

 int dfs(int s,int t,int f)
 {
     int ret=;
     if (s==t) return f;
     vis[s]=;//不要忘记这里要设置为访问过
     for (int i=;i<E[s].size();i++)
     {
         node &tmp=E[s][i];
         if (vis[tmp.to]== && tmp.cap>)
         {
             int delta=dfs(tmp.to,t,min(tmp.cap,f));
             if (delta>)
             {
                 ret+=delta;
                tmp.cap-=delta;
                E[tmp.to][tmp.pos].cap+=delta;
                f-=delta;
             }
         }
     }
     return ret;
 }

 int maxflow(int u,int v)
 {
     int flow=;
     for (;;)
     {
         memset(vis,,sizeof(vis));
         int f=dfs(u,v,INF);
         if (f==) return flow;
            else flow+=f;
     }
 }

 int main()
 {
     while(~scanf("%d%d",&n,&m))
     {
           memset(E,,sizeof(E));
           for (int i=;i<n;i++)
           {
               int x,y,z;
               scanf("%d%d%d",&x,&y,&z);
               addedge(x,y,z);
           }
           cout<<maxflow(,m)<<endl;
     }
     return ;
 }

2016/3/6更正：建立一个ret，每次递归不是找到一条增广路径就返回的..之前写的和FordFulkerson效率超不多orz