这道题需要涉及到置换群的知识，只需知道一个定理。

最小交换次数=元素个数-环的个数。

1 program pku1674(input,output); 2 var 3     number :array[0..11000] of integer; 4     v       :array[0..11000] of boolean; 5     n,cases:longint; 6     answer :longint; 7 procedure init; 8 var 9     i:longint;10 begin11     readln(n);12     for i:=1 to n do13         read(number[i]);14     fillchar(v,sizeof(v),false);15 end;{
      init }16 procedure main;17 var18     now,i:longint;19 begin20     answer:=0;21     for i:=1 to n do22     if not v[i] then23     begin24         inc(answer);25         v[i]:=true;26         now:=number[i];27         while not v[now] do28         begin29             v[now]:=true;30             now:=number[now];31         end;32     end;33 end;{
      main }34 procedure print;35 begin36     writeln(n-answer);37 end;{
      print }38 begin39     readln(cases);40     while cases>0 do41     begin42         dec(cases);43         init;44         main;45         print;46     end;47 end.