北大1611题

题目链接：http://poj.org/problem?id=1611

 

并查集简单应用

#include <iostream>
using namespace std;

int father[30000],rank[30000];

void Make(int n)
{
 int i;
 for(i = 0;i < n;++i)
 {
  father[i] = i;
  rank[i] = 1;
 }
}

int Find(int x)
{
 if(x != father[x])
  father[x] = Find(father[x]);
 return father[x];
}

void Union(int x,int y)
{
 x = Find(x);
 y = Find(y);

 if(x == y) return;
 if(rank[x] > rank[y])
 {
  father[y] = x;
  rank[x] += rank[y];
 }
 else
 {
  father[x] = y;
  rank[y] += rank[x];
 }
}

int main(int argc, char** argv)
{
 freopen("in.txt","r",stdin);

 int n,m,k,cur;
 while(scanf("%d%d",&n,&m) != EOF)
 {
  if(n == 0 && m == 0)
   break;

  Make(n);

  int i,j,next;
  for(i = 0;i < m;++i)
  {
   scanf("%d%d",&k,&cur);
   for(j = 1;j < k;++j)
   {
    scanf("%d",&next);
    Union(cur,next);
   }
  }

  printf("%d\n",rank[Find(0)]);
 }
 return 0;
}