UVA 1659 Help Little Laura (最小费用流，最小循环流)

  1 #include <bits/stdc++.h>
  2 #define LL long long
  3 #define pii pair<int,int>
  4 #define pdi pair<double,int>
  5 #define INF 0x7f7f7f7f
  6 using namespace std;
  7 const int N=200;
  8 int x[N], y[N], rudu[N];
  9 int earn, lost, n;
 10 vector<int> vect[N], vec[N];
 11 double sum;
 12 
 13 struct node
 14 {
 15     int from, to, cap, flow;
 16     double val;
 17     node(){};
 18     node(int from,int to,double val,int cap,int flow):from(from),to(to),val(val),cap(cap),flow(flow){};
 19 }edge[90000];
 20 int edge_cnt;
 21 
 22 void add_node(int from,int to,double val,int cap,int flow)
 23 {
 24     edge[edge_cnt]=node(from, to, val, cap, flow );
 25     vec[from].push_back(edge_cnt++);
 26 }
 27 
 28 void build_graph()
 29 {
 30     for(int i=1; i<=n; i++)
 31     {
 32         for(int j=0; j<vect[i].size(); j++)
 33         {
 34             int t=vect[i][j];
 35             double v= lost - sqrt( pow(x[i]-x[t],2)+pow(y[i]-y[t],2) )*earn;
 36 
 37             if(v<0)
 38             {
 39                 add_node(t, i, -v, 1, 0 );  //反边
 40                 add_node(i, t, v, 0, 0 );
 41                 sum+=v;
 42                 rudu[t]++,rudu[i]--;
 43             }
 44             else
 45             {
 46                 add_node(i, t, v, 1, 0);
 47                 add_node(t, i, -v, 0, 0);
 48             }
 49         }
 50     }
 51     for(int i=1; i<=n; i++)
 52     {
 53         if(rudu[i]>0)
 54         {
 55             add_node(0, i, 0, rudu[i], 0);
 56             add_node(i, 0, 0, 0, 0);
 57         }
 58         if(rudu[i]<0)
 59         {
 60             add_node(i, n+1, 0, -rudu[i], 0);
 61             add_node(n+1, i, 0, 0, 0);
 62         }
 63     }
 64 }
 65 
 66 int flow[N], path[N], inq[N];
 67 double cost[N];
 68 
 69 double spfa(int s,int e)
 70 {
 71     deque<int> que(1,s);
 72     cost[s]=0;
 73     flow[s]=INF;
 74     inq[s]=1;
 75     while(!que.empty())
 76     {
 77         int x=que.front();
 78         que.pop_front();
 79         inq[x]=0;
 80         for(int i=0; i<vec[x].size(); i++)
 81         {
 82             node e=edge[vec[x][i]];
 83             if(e.cap>e.flow && cost[e.to]>cost[e.from]+e.val )
 84             {
 85                 flow[e.to]=min(flow[e.from],e.cap-e.flow);
 86                 cost[e.to]=cost[e.from]+e.val;
 87                 path[e.to]=vec[x][i];
 88                 if(!inq[e.to])
 89                 {
 90                     inq[e.to]=1;
 91                     que.push_back(e.to);
 92                 }
 93             }
 94         }
 95     }
 96     return cost[e];
 97 }
 98 
 99 double mcmf(int s,int e)
100 {
101     double ans_cost=0.0;
102     while(true)
103     {
104         memset(flow,0,sizeof(flow));
105         memset(inq,0,sizeof(inq));
106         memset(path,0,sizeof(path));
107         for(int i=0; i<=e; i++)   cost[i]=1e39;
108 
109         double tmp=spfa(s,e);    //返回费用
110         if(tmp>1e38)    return  ans_cost;
111         ans_cost+=tmp;
112 
113         int ed=e;
114         while(ed!=s)
115         {
116             int t=path[ed];
117             edge[t].flow+=flow[n+1];
118             edge[t^1].flow-=flow[n+1];
119             ed=edge[t].from;
120         }
121     }
122 }
123 
124 int main()
125 {
126     freopen("input.txt", "r", stdin);
127     int b, j=0;
128     while(scanf("%d", &n), n)
129     {
130         scanf("%d%d",&earn,&lost);
131         for(int i=0; i<=n+1; i++)   vect[i].clear();
132         for(int i=0; i<=n+1; i++)   vec[i].clear();
133         memset(edge,0,sizeof(edge));
134         memset(rudu,0,sizeof(rudu));
135         edge_cnt=0;
136         sum=0;
137 
138         for(int i=1; i<=n; i++)
139         {
140             scanf("%d%d",&x[i],&y[i]);
141             while(scanf("%d",&b), b)    vect[i].push_back(b);   //原图邻接表
142         }
143         build_graph();
144         printf("Case %d: %.2f\n", ++j,  -(mcmf(0,n+1)+sum)+0.0000001 );
145     }
146     return 0;
147 }