hdu3068最长回文(Manacher算法)

var
  s1,s2:ansistring;
  s:array[0..1000000]of char;
  p:array[0..1000000]of longint;
  max,ans,mid,i,len:longint;
  ch:char;
  flag:boolean;

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

begin
  while not eof do begin
    readln(s1);
    readln(s2);
    len:=length(s1);
    fillchar(p,sizeof(p),0);
    s[0]:=‘$‘;
    s[1]:=‘#‘;
    for i:=1 to len do begin
      s[i*2]:=s1[i];
      s[i*2+1]:=‘#‘;
    end;
    len:=len*2+2;
    s[len]:=‘#‘;
    mid:=0;
    max:=0;
    ans:=1;
    for i:=1 to len do begin
      if max>i then
        p[i]:=min(p[mid*2-i],max-i)
      else p[i]:=1;
      while s[i+p[i]]=s[i-p[i]] do inc(p[i]);
      if p[i]+i>max then begin
        max:=p[i]+i;
        mid:=i;
      end;
      if ans<p[i] then ans:=p[i];
    end;
    writeln(ans-1);
  end;
end.