bzoj 1005: [HNOI2008]明明的烦恼

prufer编码的应用：

var
  a:array[1..10000]of longint;
  su,p:array[1..1000]of longint;
  b:array[1..10000]of boolean;
  ans:array[1..10000]of longint;
  i,j,m,n,s,k,w,sum,c:longint;
procedure add(t,d:longint);
var
  i:longint;
begin
  for i:=1 to s do
    while t mod su[i]=0 do
      begin
        inc(p[i],d);
        t:=t div su[i];
      end;
end;
procedure cheng(t:longint);
var
  i:longint;
begin
  for i:=1 to c do
    ans[i]:=ans[i]*t;
  for i:=1 to c-1 do
    begin
      inc(ans[i+1],ans[i] div 10);
      ans[i]:=ans[i] mod 10;
    end;
  while ans[c]>=10 do
    begin
      ans[c+1]:=ans[c] div 10;
      ans[c]:=ans[c] mod 10;
      inc(c);
    end;
end;
begin
  readln(n);
  for i:=1 to n do
    read(a[i]);
  fillchar(b,sizeof(b),true);
  for i:=2 to n do
    if b[i] then
      begin
        inc(s);
        su[s]:=i;
        for j:=1 to n div i do
          b[i*j]:=false;
      end;
  fillchar(p,sizeof(p),0);
  sum:=n-2;
  k:=n;
  for i:=1 to n do
    if a[i]<>-1 then
      begin
        for j:=1 to a[i]-1 do
          begin
            add(sum,1);
            dec(sum);
            add(j,-1);
          end;
        dec(k);
      end;
  c:=1;
  fillchar(ans,sizeof(ans),0);
  ans[1]:=1;
  for i:=1 to s do
    for j:=1 to p[i] do
      cheng(su[i]);
  for i:=1 to sum do
    cheng(k);
  for i:=c downto 1 do
    write(ans[i]);
end.