program ural1211;
const
  maxn=25000;
var
  next:array[1..maxn]of word;
  t,i:word;
procedure test;
  var
    sign:array[1..maxn]of word;
    n,i,x:word;
    zeros:byte;
  begin
    read(n);zeros:=0;
    for i:=1 to n do begin
      read(next[i]);
      if next[i]=0 then begin
        inc(zeros);
        if zeros>1 then break;
      end;
    end;
    if zeros<>1 then begin
      writeln('NO');
      exit;
    end;
    fillchar(sign,sizeof(sign),0);
    for i:=1 to n do begin
      x:=i;
      while x>0 do begin
        if sign[x]=i then begin
          writeln('NO');
          exit;
        end
        else if sign[x]>0 then
          break;
        sign[x]:=i;x:=next[x];
      end;
    end;
    writeln('YES');
  end;
begin
  read(t);
  for i:=1 to t do
    test;
end.

I too get WA#3 to this one, here is my C solution:

#include<stdio.h>
#define true 1
#define false 0
main()
{
 int parent[25001] , T , temp , temp2 , temp3 , test;
 int N , answer , cur;
 int confess , resolved;
 scanf("%d" , &T);
 for(test = 1 ; test <= T ; test++)
 {
  scanf("%d" , &N);
  confess = resolved = false;
  for(temp = 1 ; temp <= N ; temp++)
   parent[temp] = -1;
  for(temp = 1 ; temp <= N && resolved == false ; temp++)
  {
   scanf("%d" , &answer);
   if(answer == 0)
   {
    if(confess) { printf("NO\n"); resolved = true; }
    else confess = true;
   }
   else
   {
    cur = temp;
    while(cur != -1 && cur != answer) cur = parent[cur];
    if(cur == answer){  printf("NO\n") ; resolved = true; }
    else parent[answer] = temp;
   }
  }
  if(resolved == false)
   printf("YES\n");
  for( ; temp <= N ; temp++)
   scanf("%d" , &answer);
 }
}



Edited by author 24.05.2005 19:04