POJ1611->并查集

题意：求包含0元素的集合的元素个数

题解：基础并查集

#include <stdio.h>
#include <iostream>
using namespace std ;
#define MAX 30005
int parent[MAX] ;
int rank[MAX] ;
int num[MAX] ;
void make_set(int x)
{
parent[x] = x ;
rank[x] = 0 ;
num[x] = 1 ;
}
int find_set(int x)//查找x的根节点
{
int r = x , temp ;
while(parent[r] != r) r = parent[r] ;
while(x != r)
{
temp = parent[x] ;
parent[x] = r ;
x = temp ;
}
return x ;
}
void union_set(int x , int y)//合并两个集合
{
x = find_set(x) ;
y = find_set(y) ;
if(x == y) return ;
if(rank[x] > rank[y])
{
parent[y] = x ;
num[x] += num[y] ;
}
else
{
parent[x] = y ;
if(rank[x] == rank[y]) rank[y] ++ ;
num[y] += num[x] ;
}
}
int main()
{
int m , n , t , x , y;
while(scanf("%d%d",&n , &m)!= EOF , m+n)
{
if(m == 0)
{
cout << '1' << endl ;
continue ;
}
for(int i = 0 ; i < n ; i ++) make_set(i) ;
for(int i = 0 ; i < m ; i ++)
{
scanf("%d" , &t) ;
scanf("%d" , &x) ;
for (int j = 1; j < t; ++j)
{
scanf("%d" , &y) ;
union_set(x , y) ;
x = y ;
}
}
x = find_set(0) ;
cout << num[x] << endl ;
}
return 0 ;
}