2017 新疆赛区网络赛 J Our Journey of Dalian Ends 费用流

  1 #include<bits/stdc++.h>
  2 #define rep(i,a,b) for(int i=a;i<=b;i++)
  3 using namespace std;
  4 const int MAXN=101000;
  5 const int maxn=20000;
  6 const int INF=~0U>>1;
  7 int maxflow=0,cost=0;
  8 int pre[maxn],vis[maxn],dis[maxn];
  9 int S,T,S1;
 10 int n,m;
 11 int tot=0;
 12 int pointer[maxn];
 13 map<string,int> mp;
 14 int shanghai;
 15 struct Edge
 16 {
 17     int to,next,cap,f,w;
 18     Edge() {};
 19     Edge(int b,int c,int nxt,int flow,int weight) {to=b,cap=c,next=nxt,f=flow,w=weight;}
 20 }edge[MAXN];
 21 inline void addedge(int a,int b,int c,int w1)
 22 {
 23     edge[tot]=Edge(b,c,pointer[a],0,w1);
 24     pointer[a]=tot++;
 25     edge[tot]=Edge(a,0,pointer[b],0,-w1);
 26     pointer[b]=tot++;
 27 }
 28 bool spfa(int s,int t)
 29 {
 30     queue<int > q;
 31     rep(i,S,T)
 32     {
 33         dis[i]=INF;
 34         vis[i]=false;
 35         pre[i]=-1;
 36     }
 37     dis[S]=0;
 38     vis[S]=1;
 39     q.push(S);
 40     while(!q.empty())
 41     {
 42         int u=q.front();q.pop();
 43         vis[u]=0;
 44         for(int j=pointer[u];j!=-1;j=edge[j].next)
 45         {
 46             int v=edge[j].to;
 47       //      if(u==92) printf("u=92 v=%d\n",v);
 48             if(edge[j].cap-edge[j].f>0&&dis[v]>dis[u]+edge[j].w)
 49             {
 50                 dis[v]=dis[u]+edge[j].w;
 51                 pre[v]=j;
 52                 if(!vis[v])
 53                 {
 54                     vis[v]=1;q.push(v);
 55                 }
 56             }
 57         }
 58     }
 59     if(pre[T]==-1) return false;
 60     else return true;
 61 }
 62 int mcmf()
 63 {
 64     int flow=0;
 65     cost=0;
 66     while(spfa(S,T))
 67     {
 68         int mi=INF;
 69         for(int i=pre[T];i!=-1;i=pre[edge[i^1].to])
 70         {
 71             mi=min(mi,edge[i].cap-edge[i].f);
 72         }
 73         for(int i=pre[T];i!=-1;i=pre[edge[i^1].to])
 74         {
 75             edge[i].f+=mi;
 76             edge[i^1].f-=mi;
 77            // printf("edge[%d].w=%d edge[i].to=%d\n",i,edge[i].w,edge[i].to);
 78             //cost+=edge[i].w*mi;
 79         }
 80        // flow+=mi;
 81     }
 82     return flow;
 83 }
 84 void Input()
 85 {
 86     mp.clear();
 87     scanf("%d",&m);
 88     string a;
 89     string b;
 90     int len;
 91     int cnt=1;
 92     memset(pointer,-1,sizeof(pointer));
 93     tot=0;
 94     rep(i,1,m)
 95     {
 96         cin>>a>>b>>len;
 97         if(mp[a]==0)
 98         {
 99             mp[a]=cnt;
100             addedge(cnt,cnt+1,1,0);
101            // if(a=="Shanghai") shanghai=cnt;
102             cnt+=2;
103 
104         }
105         if(mp[b]==0)
106         {
107             mp[b]=cnt;
108             addedge(cnt,cnt+1,1,0);
109          //   if(b=="Shanghai") shanghai=cnt;
110             cnt+=2;
111         }
112         addedge(mp[a]+1,mp[b],INF,len);
113       //  addedge(mp[b],mp[a]+1,1,len);
114         addedge(mp[b]+1,mp[a],INF,len);
115         //addedge(mp[a],mp[b]+1,1,len);
116     }
117     S=0;T=cnt;
118    // printf("shanghai=%d\n",mp["Shanghai"]);
119     addedge(mp["Shanghai"],mp["Shanghai"]+1,1,0);
120     addedge(S,mp["Shanghai"],2,0);
121     addedge(mp["Xian"]+1,T,1,0);
122     addedge(mp["Dalian"]+1,T,1,0);
123 }
124 int main()
125 {
126    // freopen("in.txt","r",stdin);
127     int T;
128     scanf("%d",&T);
129     rep(t1,1,T)
130     {
131         Input();
132         maxflow=mcmf();
133         if(maxflow==2) printf("%d\n",cost);
134         else printf("-1\n");
135     }
136     return 0;
137 }