hdu1162 Eddy's picture 基础最小生成树

     #include <cstdio>
     #include <cmath>
     #include <cstring>
     #include <algorithm>
     #include <string>
     using namespace std;

     int n, m;
     int f[];

     struct node
     {
         int u, v;
         double w;
     }map[];

     int getf(int a)
     {
         if (f[a] == a)
         {
             return a;
         }

         f[a] = getf(f[a]);
         return f[a];
     }

     void merge(int a, int b)
     {
         int x = getf(a);
         int y = getf(b);

         if (x != y)
             f[y] = x;
     }

     void init()
     {
         for (int i = ; i <= n; i++)
             f[i] = i;
     }

     bool cmp(node a, node b)
     {
         return a.w < b.w;
     }

     double kura()
     {
         double res = ;
         sort(map, map + m, cmp);

         for (int i = ; i < m; i++)
         {
             if (getf(map[i].u) != getf(map[i].v))
             {
                 merge(map[i].u, map[i].v);
                 res += map[i].w;
             }
         }
         return res;
     }

     double a[][];

     int main()
     {
         while (scanf("%d", &n) != EOF)
         {
             m = n*(n - );
             for (int i = ; i <= n; i++)
                 scanf("%lf %lf", &a[i][], &a[i][]);

             int k = ;
             for (int i = ; i <= n; i++)
             {
                 for (int j = i + ; j <= n; j++)
                 {
                     map[k].u = i;
                     map[k].v = j;
                     map[k].w = sqrt(abs(pow(a[j][] - a[i][], ) + pow(a[j][] - a[i][], )));
                     k++;
                 }
             }
             init();
             printf("%.2lf\n", kura());
         }

         return ;
     }