hdoj 1232 畅通工程

题目链接：

http://acm.hdu.edu.cn/showproblem.php?pid=1232

/*典型的并查集习题，思路比较简单，只需要找出有几棵树就可以了*/#include <iostream>using namespace std;const int MAX = 1001;int father[MAX];int rank[MAX];void Make_Set(const int n) { for (int i = 1; i <= n ; i++) {  father[i] = i;  rank[i] = 0; }}int Find_Set(const int x) { if (father[x] != x)  father[x] = Find_Set(father[x]); return father[x];}void Union (int x, int y) { x = Find_Set(x); y = Find_Set(y); if (x == y) return ; if (rank[x] > rank[y]) father[y] = x; else if (rank[x] < rank[y]) father[x] = y; else {  rank[y]++; father[x] = y; }}int main (){ int n, m; int a, b; while (cin >> n && n) {  cin >> m;  Make_Set(n);  while (m--) {   cin >> a >> b;   Union(a, b);  }  int count = -1;  for (int i = 1; i <= n; i++)   if (father[i] == i)    count ++;  cout << count << endl; }}