【HDOJ3068】最长回文（manacher）

题意：求一个由小写字母组成的字符串中的最长回文长度

cas<=120 n<=110000

思路：试manacher板子

 var a:array[..]of char;
     p:array[..]of longint;
     ch:ansistring;
     len,n,i,mx,id,ans:longint;

 function min(x,y:longint):longint;
 begin
  if x<y then exit(x);
  exit(y);
 end;

 function max(x,y:longint):longint;
 begin
  if x>y then exit(x);
  exit(y);
 end;

 begin
  assign(input,'hdoj3068.in'); reset(input);
  assign(output,'hdoj3068.out'); rewrite(output);
  while not eof do
  begin
   readln(ch);
   len:=length(ch);
   if len= then continue;
   n:=; a[]:='@'; a[]:='#';
   for i:= to len do
   begin
    inc(n); a[n]:=ch[i];
    inc(n); a[n]:='#';
   end;
   inc(n); a[n]:='$';
   mx:=; id:=;
   for i:= to n- do
   begin
    if mx>i then p[i]:=min(p[*id-i],mx-i)
     else p[i]:=;
    while a[i+p[i]]=a[i-p[i]] do inc(p[i]);
    if p[i]+i>mx then
    begin
     mx:=p[i]+i;
     id:=i;
    end;
   end;
   ans:=;
   for i:= to n- do ans:=max(ans,p[i]-);
   writeln(ans);
  end;
  close(input);
  close(output);
 end.