SUBSTR – SPOJ

Đề bài: http://yeulaptrinh.de/319/substr-spoj/

Thuật toán:

Code:

const
  fi='';
  fo='';
  maxn=trunc(1e6);
  base=trunc(1e9)+7;
  pp=307;
var
  f : array[0..maxn] of int64;
  i,j,n,m : longint;
  hb : int64;
  a,b : array[1..maxn] of byte;
  ha,pow : array[0..maxn] of int64;
procedure enter;
var x : ansistring;
begin
  assign(input,fi);reset(input);
  readln(x);
  m := length(x);
  for i := 1 to m do a[i] := ord(x[i])-48;
  readln(x);
  n := length(x);
  for i := 1 to n do b[i] := ord(x[i])-48;
  close(input);
end;
function gethash(l,r : longint) : int64;
begin
  gethash := (ha[r]-ha[l-1]*pow[r-l+1] + base*base) mod base;
end;
procedure process;
begin
  assign(output,fo);rewrite(output);
  ha[0] := 0;
  for i:=1 to m do ha[i] := (ha[i-1]*pp + a[i]) mod base;
  pow[0] := 1;
  for i:=1 to m do pow[i] := pow[i-1]*pp mod base;
  hb := 0;
  for i:=1 to n do hb := (hb*pp + b[i]) mod base;
  for i:=1 to m-n+1 do
    if hb = gethash(i,i+n-1) then
      write(i,' ');
  close(output);
end;
begin
  enter;
  process;
end.