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[0..10100,0..80] of char;
    s:string;
    rr,cc:array[0..10100] of boolean;
    pre:array[0..10100] of longint;
procedure init;
 begin
 readln(r,c);
 for i:=1 to r do
  begin
   readln(s);
   for j:=1 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:=1 to r do
  begin
   pre[1]:=0;k:=0;
   for i:=2 to c do
    begin
     while (k<>0) and (ch[x,k+1]<>ch[x,i]) do k:=pre[k];
     if ch[x,k+1]=ch[x,i] then inc(k);
     pre[i]:=k;
    end;
   k:=c;
   for i:=0 to c do
    if c-pre[k]<>i then cc[i]:=false else k:=pre[k];
  end;
 for x:=1 to c do
  begin
   pre[1]:=0;k:=0;
   for i:=2 to r do
    begin
     while (k<>0) and (ch[k+1,x]<>ch[i,x]) do k:=pre[k];
     if ch[k+1,x]=ch[i,x] then inc(k);
     pre[i]:=k;
    end;
   k:=r;
   for i:=0 to r do
    if r-pre[k]<>i then rr[i]:=false else k:=pre[k];
  end;
  for i:=1 to r do if rr[i] then break;
  for j:=1 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？