151. [USACO Dec07] 建造路径

  1 #include<iostream>
  2 #include<cstdio>
  3 #include<cstring>
  4 #include<cmath>
  5 #include<algorithm>
  6 #define INF 0x7ffff
  7 using namespace std;
  8 const int MAXN=1001;
  9 int vis[MAXN][MAXN];// 记录两个城市之间是否已经有道路相连
 10 double dis[MAXN][MAXN]; 
 11 struct node
 12 {
 13     int u,v,nxt;
 14     double w;
 15 }edge[1000001];
 16 int f[MAXN*3];
 17 int num=1;
 18 struct pos
 19 {
 20     long long int  x,y;
 21 }where[MAXN*3];
 22 int n,m;
 23 double ans=0;
 24 int read(int & n)
 25 {
 26     int flag=0,x=0;char c='/';
 27     while(c<'0'||c>'9'){c=getchar();if(c=='-')flag=1;}
 28     while(c>='0'&&c<='9')x=x*10+(c-48),c=getchar();
 29     if(flag)n=-x;
 30     else n=x;
 31 }
 32 void deal_dis()
 33 {
 34     //for(int i=1;i<=n;i++)
 35     //    for(int j=1;j<i;j++)
 36     //        dis[i][j]=INF;
 37             
 38     for(int i=1;i<=n;i++)
 39         for(int j=1;j<i;j++)
 40             dis[i][j]=sqrt((where[i].x-where[j].x)*(where[i].x-where[j].x)+(where[i].y-where[j].y)*(where[i].y-where[j].y)); 
 41 
 42     /*for(int i=1;i<=n;i++)
 43     {
 44         for(int j=1;j<i;j++)
 45             printf("%.2lf ",dis[i][j]);
 46         printf("\n");
 47     }*/
 48     //cout<<dis[219][65];
 49 }
 50 void add_edge(int p,int q,double we)
 51 {
 52     edge[num].u=p;
 53     edge[num].v=q;
 54     edge[num].w=we;
 55 //    cout<<edge[num].w<<endl;
 56     num++;
 57 }
 58 int find(int x)
 59 {
 60     if(f[x]!=x)
 61     f[x]=find(f[x]);
 62     return f[x];
 63 }
 64 int unionn(int x,int y)
 65 {
 66     int fx=find(x);
 67     int fy=find(y);
 68     f[fx]=fy;
 69 }
 70 int comp(const node & a,const node & b)
 71 {
 72     return a.w<b.w;
 73 }
 74 void kruskal()
 75 {
 76     sort(edge+1,edge+num+1,comp);
 77     int k=1;
 78     for(int i=1;i<=num;i++)
 79     {
 80         if(find(edge[i].u)!=find(edge[i].v))
 81         {
 82             unionn(edge[i].u,edge[i].v);
 83             k++;
 84             ans=ans+edge[i].w;    
 85         }
 86         if(k==n)
 87         break;
 88     }
 89     printf("%.2lf",ans);
 90 }
 91 int main()
 92 {
 93     freopen("roads.in","r",stdin);
 94     freopen("roads.out","w",stdout);
 95     read(n);read(m);
 96     for(int i=1;i<=n;i++)
 97         cin>>where[i].x>>where[i].y,f[i]=i;
 98     
 99     for(int i=1;i<=m;i++)
100     {
101         int x,y;
102         read(x);read(y);
103         add_edge(x,y,0.00);
104         vis[x][y]=1;
105     }
106     
107     deal_dis();
108     
109     for(int i=1;i<=n;i++)
110         for(int j=1;j<i;j++)
111             if(i!=j&&vis[i][j]==0)
112             add_edge(i,j,dis[i][j]);
113     
114     kruskal();
115     return 0;
116 }