http://acm.hdu.edu.cn/showproblem.php?pid=1213

1 #include 
      
        2 #include 
       
         3 #include 
        
          4 #define maxn 2000 5 using namespace std; 6  7 int f[maxn],n,m; 8  9 void inti()10 {11     for(int i=1; i<=n; i++)12     {13         f[i]=i;14     }15 }16 17 int find1(int x)18 {19     if(x==f[x]) return x;20     return f[x]=find1(f[x]);21 }22 23 void union2(int a,int b)24 {25     int fa=find1(a);26     int fb=find1(b);27     if(fa!=fb)28     {29         f[fa]=fb;30     }31 }32 33 int main()34 {35     int t;36     scanf("%d",&t);37     while(t--)38     {39         scanf("%d%d",&n,&m);40         inti();41         for(int i=1; i<=m; i++)42         {43             int a1,b1;44             scanf("%d%d",&a1,&b1);45             union2(a1,b1);46         }47         int ans=0;48         for(int i=1; i<=n; i++)49         {50             if(f[i]==i) ans++;51         }52         printf("%d\n",ans);53     }54     return 0;55 }