Wireless Network POJ - 2236 (并查集)

 #include<iostream>
 #include<vector>
 #include<string>
 #include<cmath>
 #include<algorithm>
 #include<cstdio>
 #include<cstring>

 using namespace std;

 int n, d;
 double dis[][];
 struct Point
 {
     double x, y;
 }cur[];

 int Tree[];

 int findRoot(int x)
 {
     if(Tree[x] == -)
         return x;
     int tmp = findRoot(Tree[x]);
     Tree[x] = tmp;
     return tmp;
 }

 int main()
 {
     scanf("%d %d", &n, &d);
     for(int i = ; i <= n; ++i)
     {
         Tree[i] = -;
         double x, y;
         scanf("%lf %lf", &x, &y);
         cur[i].x = x;
         cur[i].y = y;
     }

     for(int i = ; i <= n; ++i)
         for(int j = i; j <= n; ++j)
         {
             dis[i][j] = dis[j][i] = sqrt((cur[i].x - cur[j].x)*(cur[i].x - cur[j].x)+(cur[i].y - cur[j].y)*(cur[i].y - cur[j].y));
         }

     vector<int> rep;    // repaired
     char c;
     while(scanf("%c", &c) != EOF)
     {
         if(c == 'O')
         {
             int t;
             scanf("%d", &t);
             for(int i = ; i < rep.size(); ++i)
             {
                 if(dis[rep[i]][t] <= d)
                 {
                     /* 不能这样写，否则会导致并查集的树结构不好，
                        路径压缩次数过多，导致RuntimeError(栈溢出)
                     int ri = findRoot(rep[i]);
                     Tree[ri] = t;
                     */

                     // 标准写法
                     int ri = findRoot(rep[i]);
                     int rt = findRoot(t);
                     if(ri != rt)
                         Tree[ri] = rt;

                 }
             }
             rep.push_back(t);

         }
         else if(c == 'S')
         {
             int t1, t2;
             scanf("%d %d", &t1, &t2);
             int rt1 = findRoot(t1);
             int rt2 = findRoot(t2);
             if(rt1 == rt2)
                 printf("SUCCESS\n");
             else
                 printf("FAIL\n");
         }
     }

     return ;
 }