hdu1875 畅通工程再续 暴力+基础最小生成树

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

 const int maxn = ;
 const int L = ;
 const int R = ;
 int t, n, m, ans;
 double total;
 struct node
 {
     int x, y;
     int cost;
 }pot[maxn];
 int fa[maxn];
 int px[maxn], py[maxn];

 int cal()
 {
     int i, j, tx, ty, len, pos;
     pos = ;
     for (i = ; i<n; i++)
     {
         for (j = i + ; j<n; j++)
         {
             tx = px[i] - px[j];
             ty = py[i] - py[j];
             len = tx*tx + ty*ty;
             if (len >= L&&len <= R)
             {
                 pot[pos].x = i;
                 pot[pos].y = j;
                 pot[pos].cost = len;
                 pos++;
             }
         }
     }
     return pos;
 }

 void init()
 {
     total = 0.0;
     ans = n - ;
     for (int i = ; i <= n; i++)
     {
         fa[i] = i;
     }
 }

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

 int find(int x)
 {
     if (x != fa[x])
         return fa[x] = find(fa[x]);
     return fa[x];
 }

 int join(int x, int y)
 {
     int flag = ;
     if (x != y)
     {
         ans--;
         fa[x] = y;
         flag = ;
     }
     return flag;
 }

 int main()
 {
     scanf("%d", &t);
     while (t--)
     {
         scanf("%d", &n);
         init();
         for (int i = ; i<n; i++)
         {
             scanf("%d %d", &px[i], &py[i]);
         }
         int len = cal();
         if (len<n - )
         {
             printf("oh!\n");
             continue;
         }
         sort(pot, pot + len, cmp);
         for (int i = ; i<len; i++)
         {
             int fx, fy;
             fx = find(pot[i].x);
             fy = find(pot[i].y);
             if (join(fx, fy) == )
             {
                 total += sqrt(pot[i].cost*1.0);
             }
         }
         if (ans != )
         {
             printf("oh!\n");
             continue;
         }
         printf("%.1lf\n", total * );
     }
     return ;
 }