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。

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <queue>
 4 #include <vector>
 5 #define maxn 2010
 6 #define oo 0x3f3f3f3f
 7 using namespace std;
 8
 9 struct Edge {
10     int u, v, c, f;
11     Edge( int u, int v, int c, int f ):u(u),v(v),c(c),f(f){}
12 };
13 struct Mcmf {
14     int n, src, dst;
15     vector<Edge> edge;
16     vector<int> g[maxn];
17     int dis[maxn], pth[maxn], ext[maxn];
18
19     void init( int n, int src, int dst ) {
20         this->n = n;
21         this->src = src;
22         this->dst = dst;
23         for( int u=1; u<=n; u++ )
24             g[u].clear();
25         edge.clear();
26     }
27     void add_edge( int u, int v, int c, int f ) {
28         g[u].push_back( edge.size() );
29         edge.push_back( Edge(u,v,c,f) );
30         g[v].push_back( edge.size() );
31         edge.push_back( Edge(v,u,-c,0) );
32     }
33     bool spfa( int &flow, int &cost ) {
34         queue<int> qu;
35         memset( dis, 0x3f, sizeof(dis) );
36         qu.push( src );
37         dis[src] = 0;
38         pth[src] = -1;
39         ext[src] = true;
40         while( !qu.empty() ) {
41             int u=qu.front();
42             qu.pop();
43             ext[u] = false;
44             for( int t=0; t<g[u].size(); t++ ) {
45                 Edge &e = edge[g[u][t]];
46                 if( e.f && dis[e.v]>dis[e.u]+e.c ) {
47                     dis[e.v] = dis[e.u]+e.c;
48                     pth[e.v] = g[u][t];
49                     if( !ext[e.v] ) {
50                         ext[e.v] = true;
51                         qu.push( e.v );
52                     }
53                 }
54             }
55         }
56         if( dis[dst]==oo ) return false;
57         int flw = oo;
58         for( int eid=pth[dst]; eid!=-1; eid=pth[edge[eid].u] )
59             flw = min( flw, edge[eid].f );
60         for( int eid=pth[dst]; eid!=-1; eid=pth[edge[eid].u] ) {
61             edge[eid].f -= flw;
62             edge[eid^1].f += flw;
63         }
64         flow += flw;
65         cost += flw*dis[dst];
66         return true;
67     }
68     bool mcmf( int &flow, int &cost ) {
69         flow = cost = 0;
70         while(spfa(flow,cost));
71         return true;
72     }
73 };
74
75 int n, m;
76 Mcmf M;
77
78 int main() {
79     int T;
80     scanf( "%d", &T );
81     for( int cas=1; cas<=T; cas++ ) {
82         printf( "Case %d: ", cas );
83         scanf( "%d%d", &n, &m );
84         M.init( n+n+2, n+n+1, n+n+2 );
85         for( int i=1,u,v,w; i<=m; i++ ) {
86             scanf( "%d%d%d", &u, &v, &w );
87             M.add_edge( u, v+n, w, 1 );
88             M.add_edge( v, u+n, w, 1 );
89         }
90         for( int u=1; u<=n; u++ ) {
91             M.add_edge( M.src, u, 0, 1 );
92             M.add_edge( u+n, M.dst, 0, 1 );
93         }
94         int flow, cost;
95         M.mcmf( flow, cost );
96         if( flow!=n ) printf( "NO\n" );
97         else printf( "%d\n", cost );
98     }
99 }