bzoj 3876 [Ahoi2014]支线剧情（有上下界的最小费用流）

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<queue>
 4 #include<vector>
 5 #define FOR(a,b,c) for(int a=(b);a<=(c);a++)
 6 using namespace std;
 7 
 8 typedef long long LL ;
 9 const int maxn = 1000+10;
10 const int INF = 1e9;
11 
12 struct Edge{ int u,v,cap,flow,cost;
13 };
14 
15 struct MCMF {
16     int n,m,s,t;
17     int inq[maxn],a[maxn],d[maxn],p[maxn];
18     vector<int> G[maxn];
19     vector<Edge> es;
20     
21     void init(int n) {
22         this->n=n;
23         es.clear();
24         for(int i=0;i<n;i++) G[i].clear();
25     }
26     void AddEdge(int u,int v,int cap,int cost) {
27         es.push_back((Edge){u,v,cap,0,cost});
28         es.push_back((Edge){v,u,0,0,-cost});
29         m=es.size();
30         G[u].push_back(m-2);
31         G[v].push_back(m-1);
32     }
33     
34     bool SPFA(int s,int t,int& flow,LL& cost) {
35         for(int i=0;i<n;i++) d[i]=INF;
36         memset(inq,0,sizeof(inq));
37         d[s]=0; inq[s]=1; p[s]=0; a[s]=INF; 
38         queue<int> q; q.push(s);
39         while(!q.empty()) {
40             int u=q.front(); q.pop(); inq[u]=0;
41             for(int i=0;i<G[u].size();i++) {
42                 Edge& e=es[G[u][i]];
43                 int v=e.v;
44                 if(e.cap>e.flow && d[v]>d[u]+e.cost) {
45                     d[v]=d[u]+e.cost;
46                     p[v]=G[u][i];
47                     a[v]=min(a[u],e.cap-e.flow);        //min(a[u],..)
48                     if(!inq[v]) { inq[v]=1; q.push(v);
49                     }
50                 }
51             }
52         }
53         if(d[t]==INF) return false;
54         flow+=a[t] , cost += (LL) a[t]*d[t];
55         for(int x=t; x!=s; x=es[p[x]].u) {
56             es[p[x]].flow+=a[t]; es[p[x]^1].flow-=a[t];
57         }
58         return true;
59     }
60     int Mincost(int s,int t,LL& cost) {
61         int flow=0; cost=0;
62         while(SPFA(s,t,flow,cost)) ;
63         return flow;
64     }
65 } mc;
66 
67 int n;
68 
69 int main() {
70     scanf("%d",&n);
71     mc.init(n+2);
72     int s=0,t=n+1;
73     mc.AddEdge(t,s,INF,0);
74     FOR(u,1,n) {
75         int m,v,c; scanf("%d",&m);
76         if(u!=1) mc.AddEdge(u,1,INF,0);
77         mc.AddEdge(u,t,m,0);
78         FOR(j,1,m) {
79             scanf("%d%d",&v,&c);
80             mc.AddEdge(u,v,INF,c);
81             mc.AddEdge(s,v,1,c);
82         }
83     }
84     LL cost;
85     mc.Mincost(s,t,cost);
86     printf("%lld\n",cost);
87     return 0;
88 }