POJ.2236 Wireless Network

1.Problem
http://poj.org/problem?id=2236

2.Idea
Using Disjoint set/Union-find set

3.Source

 double x[1003], y[1003];  
 int n;  
 double d;  
 bool g[1003][1003];  
 bool on[1003];  
 int Parent[1004];  
 int Size[1004];  
 void make_set(int v) {  
      Parent[v] = v;  
      Size[v] = 1;  
 }  
 int find_set(int v) {  
      if (v == Parent[v])  
           return v;  
      return Parent[v] = find_set(Parent[v]);  
 }  
 void union_sets(int a, int b) {  
      a = find_set(a);  
      b = find_set(b);  
      if (a != b) {  
           if (Size[a] < Size[b])  
                swap(a, b);  
           Parent[b] = a;  
           Size[a] += Size[b];  
      }  
 }  
 double dist(double x1, double x2, double y1, double y2)  
 {  
      return sqrt(pow(x1 - x2, 2) + pow(y1 - y2, 2));  
 }  
 int main()  
 {  
      cin >> n >> d;  
      for (int i = 0; i < n; i++) {  
           cin >> x[i] >> y[i];  
           make_set(i);  
      }  
      for(int i=0;i<n;i++)  
           for (int j = 0; j < n; j++) {  
                if (dist(x[i] , x[j] , y[i] , y[j]) <= d) {  
                     g[i][j] = g[j][i] = true;  
                }  
           }  
      char c;  
      while (cin >> c) {  
           int p, q;  
           if (c == 'O') {  
                cin >> p; p--;  
                on[p] = 1;  
                for (int i = 0; i < n; i++) {  
                     if (g[p][i] && p != i && on[i]) {  
                          union_sets(p, i);  
                     }  
                }  
           }  
           else if (c == 'S') {  
                cin >> p >> q; p--; q--;  
                if (find_set(p) == find_set(q)) {  
                     cout << "SUCCESS" << endl;  
                }  
                else {  
                     cout << "FAIL" << endl;  
                }  
           }  
           else {  
                break;  
           }  
      }  
      return 0;  
 }