HDU---1213（How Many Tables，并查集判连通分支数）

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<queue>
#include<string>
#include<cstring>
#include<vector>
#include<functional>
#include<utility>
#include<set>
#include<map>
#include<cmath>

using namespace std;

const int maxn=1005;
int pa[maxn];
int findset(int x)
{
return pa[x]==-1?x:pa[x]=findset(pa[x]);
}

void unionset(int x, int y)
{
int rx=findset(x);
int ry=findset(y);
if(rx==ry)return;
pa[rx]=ry;
}

int main()
{
int t;cin>>t;
while(t--)
{
int n,m;cin>>n>>m;

memset(pa,-1,sizeof(pa));

while(m--)
{   int x,y;
scanf("%d%d",&x,&y);
unionset(x,y);
}
int ans=0;
for(int i=1;i<=n;i++)
if(pa[i]<0)ans++;
cout<<ans<<endl;
}

}