slides_c.tex

数据挖掘中de一个算法 hamster的实例

\documentstyle[german,a4]{article}
\pagestyle{empty}
\advance\topmargin-20mm
\textwidth240mm
\textheight190mm
\advance\oddsidemargin-10mm

\begin{document}
\special{landscape}
\LARGE

\begin{verbatim}
/*----------------------------------------------------------------------
  Type Definitions
----------------------------------------------------------------------*/
typedef struct hamster HAMSTER; /* a hamster */

/*----------------------------------------------------------------------
  Functions
----------------------------------------------------------------------*/
/* --- enquiries --- */
extern void hms_pos  (HAMSTER *hms, int *x, int *y);
extern int  hms_dir  (HAMSTER *hms);
extern int  hms_load (HAMSTER *hms);
extern int  hms_corn (HAMSTER *hms);
extern int  hms_look (HAMSTER *hms);

/* --- actions --- */
extern int  hms_move (HAMSTER *hms);
extern void hms_turn (HAMSTER *hms, int turn);
extern int  hms_take (HAMSTER *hms, int amount);
extern int  hms_drop (HAMSTER *hms, int amount);

/* --- function to be provided by user --- */
extern void hms_ctrl (HAMSTER *hms);
\end{verbatim}

\newpage\vspace*{-15mm}
\begin{verbatim}
/*----------------------------------------------------------------------
  Preprocessor Definitions
----------------------------------------------------------------------*/
#define HMS_MAXXEXT   64        /* maximal x-extension of maze */
#define HMS_MAXYEXT   64        /* maximal y-extension of maze */
#define HMS_MAXLOAD   12        /* maximal load of corn in cheeks */
#define HMS_MAXCORN  255        /* maximal size of corn heap */

/* --- results of hms_dir() --- */
#define HMS_EAST       0        /* hamster is looking east */
#define HMS_NORTH      1        /* hamster is looking north */
#define HMS_WEST       2        /* hamster is looking west */
#define HMS_SOUTH      3        /* hamster is looking south */

/* --- results of hms_look() --- */
#define HMS_EMPTY      0        /* there is an empty field ahead */
#define HMS_CORN       1        /* there is a field with corn ahead */
#define HMS_WALL       2        /* there is a wall ahead */

/* --- parameters of hms_turn() --- */
#define HMS_POS        1        /* positive turn (counterclockwise) */
#define HMS_NEG       -1        /* negative turn (clockwise) */
#define HMS_LEFT       1        /* left     turn (counterclockwise) */
#define HMS_RIGHT     -1        /* right    turn (clockwise) */
\end{verbatim}

\newpage
\begin{verbatim}
void hms_ctrl (HAMSTER *hms)
{                               /* --- hamster control function */
  int x, y;                     /* coordinates of current field */
  int movecnt = 0;              /* number of moves made */
  int turn;                     /* turn direction (HMS_POS/HMS_NEG) */

  while (movecnt < 50) {        /* make 50 (field to field) moves */
    hms_pos(hms, &x, &y);       /* get current position in maze */
    if ((x == 0) && (y == 0))   /* if we are at home (initial pos.), */
      hms_drop(hms, HMS_MAXLOAD);    /* drop all the corn we have */
    else if (hms_corn(hms))     /* if there is corn on the field, */
      hms_take(hms, HMS_MAXLOAD);    /* take as much as we can carry */
    if ((hms_look(hms) == HMS_WALL)  /* if direction is blocked */
    ||  (RAND_MAX/4 -rand() > 0)) {  /* or just because its funny */
      turn = (RAND_MAX/2 -rand() > 0) ? HMS_POS : HMS_NEG;
      do { hms_turn(hms, turn); /* turn hamster in random direction */
      } while (hms_look(hms) == HMS_WALL);
    }                           /* until no wall blocks the way */
    hms_move(hms); movecnt++;   /* move hamster forward */
  }                             /* and count the move made */
}  /* hms_ctrl() */
\end{verbatim}

\end{document}