hdu-1232 畅通工程---并查集

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 const int maxn = 1000 + 10;
 4 int p[maxn];
 5 int n, m;
 6 set<int>s;
 7 void init()
 8 {
 9     s.clear();
10     for(int i = 0; i < maxn; i++)p[i] = i;
11 }
12 int Find(int x)
13 {
14     return x == p[x] ? x : p[x] = Find(p[x]);
15 }
16 int main()
17 {
18     while(scanf("%d", &n) != EOF && n)
19     {
20         int x, y;
21         init();
22         scanf("%d", &m);
23         while(m--)
24         {
25             scanf("%d%d", &x, &y);
26             p[Find(x)] = Find(y);
27         }
28         for(int i = 1; i <= n; i++)
29         {
30             s.insert(Find(i));
31         }
32         cout<<(s.size() - 1)<<endl;
33     }
34     return 0;
35 }