01分数规划+prim POJ2728 Desert King

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<algorithm>
 5 #include<cmath> 
 6 using namespace std;
 7 const double acc=1e-7;
 8 const double inf=1e15;
 9 int n;
10 struct data{
11     double x,y,z;
12 }node[1010];
13 double l,r,mid;
14 double dis[1010][1010],h[1010][1010],w[1010];
15 bool check[1010];
16 double ds(double x1,double y1,double x2,double y2){
17     return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
18 }
19 double prim(double c){//coefficient-系数 
20     double ret=0.0;
21     for(int i=1;i<=n;i++) w[i]=inf;//double 赋初值 
22     memset(check,0,sizeof(check));
23     w[1]=0.0;
24     for(int i=1;i<=n;i++){
25         double mn=inf;
26         int k;
27         for(int j = 1;j<=n;j++)
28             if(!check[j]&&w[j]<mn) mn=w[j],k=j;
29         check[k]=1;
30         ret+=mn;
31         for(int j=1;j<=n;j++)
32             if(!check[j]&&w[j]>h[k][j]-c*dis[k][j]) 
33                 w[j]=h[k][j]-c*dis[k][j];
34     }
35     return ret;
36 }
37 int main(){
38     while(scanf("%d",&n)){
39         if(!n) return 0;
40         for(int i=1;i<=n;i++){
41             scanf("%lf%lf%lf",&node[i].x,&node[i].y,&node[i].z);
42             for(int j=1;j<=i;j++){
43                 dis[i][j]=dis[j][i]=ds(node[i].x,node[i].y,node[j].x,node[j].y);
44                 h[i][j]=h[j][i]=abs(node[i].z-node[j].z);
45             }
46         }
47         l=0.0;
48         r=10000.0;
49         while(r-l>acc){
50             mid=(l+r)*1.0/2;
51             if(prim(mid)>0) l=mid;
52             else r=mid;
53         }
54         printf("%.3f\n",mid);
55     }
56 }