{$I-,Q-,R-,S-}

const maxn = 250000+10;

var a : array [1..maxn] of record
                             st1, st2 : string[10];
                             n1, n2   : longint;
                           end;
    d, fa, rank : array [1..maxn*2] of longint;
    name : array [1..600020] of record
                                  name : string[10];
                                  code : longint;
                                end;
    n, m, now : longint;
  
function findpa( p : longint ): longint;
  begin
    if fa[p] = p
      then findpa := p
      else begin
           fa[p] := findpa( fa[p] );
           findpa := fa[p];
           end;
  end;

procedure union( a,b : longint );
  begin
    if rank[a] > rank[b]
      then fa[b] := a
      else begin
           fa[a] := b;
           if rank[b] = rank[a] then inc( rank[b] );
           end;
  end;
  
function hash( st : string ): longint;
  var i, h, g : longint;
  begin
    h := 0;
    for i := 1 to length(st) do
      begin
      h := h shl 4 + ord( st[i] );
      g := h and ($f0000000);
      if g>0 then h := h xor( g shr 24 );
      h := h and (not g);
      end;
    h := h mod m;
    hash := h;
    {h := 0;
    for i := 1 to length(st) do
      h := (h*256 + ord( st[i] )) mod m;}
  end;
  
procedure assign_code( st : string[10]; var p : longint );
  var posi : longint;
  begin
    posi := hash( st ) mod m;
    {writeln( posi );}
    while (name[ posi ].name <> st)and(name[posi].code<>0) do
      posi := (posi + 1) mod m;
    if name[ posi ].code = 0
      then begin
           name[ posi ].name := st; name[ posi ].code := now + 1;
           inc( now ); p := now;
           end
      else p := name[ posi ].code;
  end;
  
function prime( p : longint ): boolean;
  var i : longint;
  begin
    prime := false;
    for i := 2 to trunc( sqrt(p) ) do
      if p mod i = 0
        then exit;
    prime := true;
  end;

procedure init;
  var i, j   : longint;
      st  : string;
  begin
    randomize;
    i := 0;
    st := '';
    while not seekeof(input) do
      begin
      inc( i );
      readln( st );
      while st[ length(st) ] = ' ' do
        delete( st, length(st), 1 );
      j := pos( ' ', st );
      a[i].st1 := copy( st, 1, j-1 );
      
      delete( st, 1, j );
      a[i].st2 := st;
      
      while length(a[i].st1)<9 do
        a[i].st1 := ' ' + a[i].st1 ;
        
      while length(a[i].st2)<9 do
        a[i].st2 := ' ' + a[i].st2 ;
      end;

    n := i;
    m := round( 2*n*1.2 );
    while not prime(m) do
      inc( m );

    for i := 1 to n do
      begin
      assign_code( a[i].st1, a[i].n1 );
      assign_code( a[i].st2, a[i].n2 );
      {writeln( a[i].n1,' ', a[i].n2 );}
      end;
    {close( input ); close( output ); halt}
  end;
      
procedure work;
  var i, j, p, q, pa, count    : longint;
  begin
    fillchar( d, sizeof(d), 0 );
    fillchar( fa, sizeof(fa), 0 );
    fillchar( rank, sizeof(rank), 0 );
    for i := 1 to now do
      fa[i] := i;

    for i := 1 to n do
      begin
      p := findpa( a[i].n1 );
      q := findpa( a[i].n2 );
      union( p, q );
      inc( d[ a[i].n1 ] ); inc( d[ a[i].n2 ] );
      end;

    count := 0;
    pa := findpa( 1 );
    if odd( d[1] ) then inc( count );
    for i := 2 to now do
      begin
      j := findpa( i );
      if j<>pa
        then begin
             writeln( 'Impossible' ); exit;
             end;
      if odd( d[i] ) then inc( count );
      end;
    if (count<>2)and(count<>0)
      then begin
           writeln( 'Impossible' ); exit;
           end;
    writeln( 'Possible' );
  end;
  
begin
  {assign( input,'2513.in' );
  reset( input );
  assign( output,'2513.out' );
  rewrite( output );}
  
  init;
  work;
  
  {close( input );
  close( output );}
end.

• 看pascal很费劲 (4254) sunmoonstar_love 2005-08-23 18:55:43
• Re:您有空的话帮忙看一下。。。。 (452) sunmoonstar_love 2005-08-23 18:57:26
  • 还是TLE...但是您能帮忙看程序。。已经很感谢您了 (0) fujieyun 2005-08-23 19:04:13
    • 我不懂pascal，不过建议你把每个字符串的长度存好，不要用一次算一次 (0) sunmoonstar_love 2005-08-23 19:15:47
      • 可是我每个字符串也只算了一次。。。。。 (0) fujieyun 2005-08-23 19:26:23
        • 这题好像有个空输入文件?这个会不会死循环? (0) ArXoR 2005-08-23 19:34:26
          • 空输入是0s出possible.... (0) fujieyun 2005-08-23 20:09:17
          • 居然会有空输入..... (0) FinalLaugh 2005-08-31 23:11:59