hdu 3435 图回路分割

将一个无向图分成许多回路，回路点交集为空，点幷集为V。幷最小化回路边权和。

 #include <cstdio>
 #include <cstring>
 #include <queue>
 #include <vector>
 #define maxn 2010
 #define oo 0x3f3f3f3f
 using namespace std;

 struct Edge {
     int u, v, c, f;
     Edge( int u, int v, int c, int f ):u(u),v(v),c(c),f(f){}
 };
 struct Mcmf {
     int n, src, dst;
     vector<Edge> edge;
     vector<int> g[maxn];
     int dis[maxn], pth[maxn], ext[maxn];

     void init( int n, int src, int dst ) {
         this->n = n;
         this->src = src;
         this->dst = dst;
         for( int u=; u<=n; u++ )
             g[u].clear();
         edge.clear();
     }
     void add_edge( int u, int v, int c, int f ) {
         g[u].push_back( edge.size() );
         edge.push_back( Edge(u,v,c,f) );
         g[v].push_back( edge.size() );
         edge.push_back( Edge(v,u,-c,) );
     }
     bool spfa( int &flow, int &cost ) {
         queue<int> qu;
         memset( dis, 0x3f, sizeof(dis) );
         qu.push( src );
         dis[src] = ;
         pth[src] = -;
         ext[src] = true;
         while( !qu.empty() ) {
             int u=qu.front();
             qu.pop();
             ext[u] = false;
             for( int t=; t<g[u].size(); t++ ) {
                 Edge &e = edge[g[u][t]];
                 if( e.f && dis[e.v]>dis[e.u]+e.c ) {
                     dis[e.v] = dis[e.u]+e.c;
                     pth[e.v] = g[u][t];
                     if( !ext[e.v] ) {
                         ext[e.v] = true;
                         qu.push( e.v );
                     }
                 }
             }
         }
         if( dis[dst]==oo ) return false;
         int flw = oo;
         for( int eid=pth[dst]; eid!=-; eid=pth[edge[eid].u] )
             flw = min( flw, edge[eid].f );
         for( int eid=pth[dst]; eid!=-; eid=pth[edge[eid].u] ) {
             edge[eid].f -= flw;
             edge[eid^].f += flw;
         }
         flow += flw;
         cost += flw*dis[dst];
         return true;
     }
     bool mcmf( int &flow, int &cost ) {
         flow = cost = ;
         while(spfa(flow,cost));
         return true;
     }
 };

 int n, m;
 Mcmf M;

 int main() {
     int T;
     scanf( "%d", &T );
     for( int cas=; cas<=T; cas++ ) {
         printf( "Case %d: ", cas );
         scanf( "%d%d", &n, &m );
         M.init( n+n+, n+n+, n+n+ );
         for( int i=,u,v,w; i<=m; i++ ) {
             scanf( "%d%d%d", &u, &v, &w );
             M.add_edge( u, v+n, w,  );
             M.add_edge( v, u+n, w,  );
         }
         for( int u=; u<=n; u++ ) {
             M.add_edge( M.src, u, ,  );
             M.add_edge( u+n, M.dst, ,  );
         }
         int flow, cost;
         M.mcmf( flow, cost );
         if( flow!=n ) printf( "NO\n" );
         else printf( "%d\n", cost );
     }
 }