poj 2185 （KMP)

完全不会啊……

附一份题解：http://blog.sina.com.cn/s/blog_69c3f0410100tyjl.html

 var i,j,k,r,c,x:longint;
     ch:array[..,..] of char;
     s:string;
     rr,cc:array[..] of boolean;
     pre:array[..] of longint;
 procedure init;
  begin
  readln(r,c);
  for i:= to r do
   begin
    readln(s);
    for j:= to c do ch[i,j]:=s[j];
   end;
  end;
 procedure main;
  begin
  fillchar(rr,sizeof(rr),true);
  fillchar(cc,sizeof(cc),true);
  for x:= to r do
   begin
    pre[]:=;k:=;
    for i:= to c do
     begin
      while (k<>) and (ch[x,k+]<>ch[x,i]) do k:=pre[k];
      if ch[x,k+]=ch[x,i] then inc(k);
      pre[i]:=k;
     end;
    k:=c;
    for i:= to c do
     if c-pre[k]<>i then cc[i]:=false else k:=pre[k];
   end;
  for x:= to c do
   begin
    pre[]:=;k:=;
    for i:= to r do
     begin
      while (k<>) and (ch[k+,x]<>ch[i,x]) do k:=pre[k];
      if ch[k+,x]=ch[i,x] then inc(k);
      pre[i]:=k;
     end;
    k:=r;
    for i:= to r do
     if r-pre[k]<>i then rr[i]:=false else k:=pre[k];
   end;
   for i:= to r do if rr[i] then break;
   for j:= to c do if cc[j] then break;
   writeln(i*j);
   end;
 begin
  init;
  main;
 end.             

if c-pre[k]<>i then cc[i]:=false else k:=pre[k];

if r-pre[k]<>i then rr[i]:=false else k:=pre[k];

这两句话到底什么意思？