poj2253

 1 #include <iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<cmath>
 5 using namespace std;
 6 const int maxs = 200+5;
 7 const float INF = (1<<30)-1;
 8 int N;
 9 float edge[maxs][maxs];
10 int point[maxs][2];
11 void init()
12 {
13     for(int i=1;i<=N;i++)
14         for(int j=1;j<=N;j++)
15             edge[i][j]=sqrt((point[i][0]-point[j][0])*(point[i][0]-point[j][0])+(point[i][1]-point[j][1])*(point[i][1]-point[j][1]));
16 }
17 float prim()
18 {
19     init();
20     bool vis[maxs];
21     memset(vis,false,sizeof(vis));
22     vis[1]=true;
23     float lowcost[maxs],ans=0.0;
24     for(int i=1;i<=N;i++)
25         lowcost[i]=edge[1][i];
26     for(int i=2;i<=N;i++)
27     {
28         float mins = INF;
29         int k=0;
30         for(int j=1;j<=N;j++)
31             if(!vis[j]&&lowcost[j]<mins)
32             {
33                 mins=lowcost[j];
34                 k=j;
35             }
36         if(mins>ans)
37             ans=mins;
38         if(k==2)//k=2时已经到达终点不需再找，自己也是在这个地方wa了n次，继续找就有可能更新掉答案
39             break;
40         vis[k]=true;
41         for(int j=1;j<=N;j++)
42             if(!vis[j]&&edge[k][j]<lowcost[j])
43                 lowcost[j]=edge[k][j];
44     }
45     return ans;
46 }
47 int main()
48 {
49     freopen("in.txt","r",stdin);
50     int T=1;
51     while(scanf("%d",&N)!=EOF&&N)
52     {
53         memset(point,0,sizeof(point));
54         memset(edge,0,sizeof(edge));
55         for(int i=1;i<=N;i++)
56             scanf("%d%d",&point[i][0],&point[i][1]);
57         getchar();
58         printf("Scenario #%d\n",T++);
59         printf("Frog Distance = %.3f\n\n",prim());
60     }
61     return 0;
62 }