Poj Solution 1674

http://poj.org/problem?id=1674

//* @author: 82638882@163.com
import java.io.*;
import java.util.*;
public class Main
{
 public static void main(String[] args) throws IOException
 {
  InputStreamReader is=new InputStreamReader(System.in);
  BufferedReader in=new BufferedReader(is);
  String[] ss;
  int a=Integer.parseInt(in.readLine());
  HashSet< Integer> hs=new HashSet< Integer>();
  while((a--)!=0)
  {
    int b=Integer.parseInt(in.readLine());
    ss=in.readLine().split(" ");
    int[] arr=new int[b+1];
    for(int i=0;i< b;i++)
        arr[i+1]=Integer.parseInt(ss[i]);
    int c=0;
    for(int i=1;i<=b;i++)
    {
         int u=arr[i];
    if(!hs.contains(u))
    {
     while(!hs.contains(u))
      {
        hs.add(u);
        u=arr[u];
       }
       c++;
     }
       }
    System.out.println(b-c);
    hs.clear();
    }
  }        
}