Пребарување BFS - принц принцеза

(defun run-breadth (start goal moves)
  (declare (special *open*))
  (declare (special *closed*))
  (declare (special *goal*))
  (setq *open* (list (build-record start nil)))
  (setq *closed* nil)
  (setq *goal* goal)
  (breadth-first moves))

;;; These functions handle the creation and access of (state parent)
;;; pairs.

(defun build-record (state parent) (list state parent))

(defun get-state (state-tuple) (nth 0 state-tuple))

(defun get-parent (state-tuple) (nth 1 state-tuple))

(defun retrieve-by-state (state list)
  (cond ((null list) nil)
        ((equal state (get-state (car list))) (car list))
        (t (retrieve-by-state state (cdr list)))))



(defun breadth-first (moves)
  (declare (special *open*))
  (declare (special *closed*))
  (declare (special *goal*))
  (cond ((null *open*) nil)
        (t (let ((state (car *open*)))
             (setq *closed* (cons state *closed*))

             (cond
    ;;; found solution: print path to it
        ((equal (get-state state) *goal*) (reverse (build-solution *goal*)))

            ;;; try next child state
                (t (setq *open*
                            (append (cdr *open*)
                                    (generate-descendants (get-state state)
                                                          moves)))
                      (breadth-first moves)))))))

(defun generate-descendants (state moves)
  (declare (special *open*))
  (declare (special *closed*))
  (cond ((null moves) nil)
        (t (let ((child (funcall (car moves) state))
                 (rest (generate-descendants state (cdr moves))))
             (cond ((null child) rest)
                   ((retrieve-by-state child rest) rest)
                   ((retrieve-by-state child *open*) rest)
                   ((retrieve-by-state child *closed*) rest)
                   (t (cons (build-record child state) rest)))))))


(defun build-solution (state)
  (declare (special *closed*))
  (cond ((null state) nil)
        (t (cons state (build-solution
                        (get-parent
                         (retrieve-by-state state *closed*)))))))

(defvar *initial* '((0 2) (4 0) ((0 0) (3 3)) ((2 2) (2 3 (3 2)))))


(setq *prince* (car *initial*))
(setq *queen* (cadr *initial*))
(setq *ghostlist* (caddr *initial*))
(setq *dragonlist* (cadddr *initial*))


(defun make-state (x y)
    (list x y)
    )


(defun safeFromDragons (state *dragonlist*)
    (cond
        ((null *dragonlist*) t)
        ((or(equal state (make-state (+ 1 (caar *dragonlist*))(cadar *dragonlist*)))
           (equal state (make-state (- (caar *dragonlist*) 1)(cadar *dragonlist*)))
           (equal state (make-state (caar *dragonlist*)(+ 1 (cadar *dragonlist*))))
           (equal state (make-state (caar *dragonlist*)(- (cadar *dragonlist*) 1)))
           (equal state (make-state (+ 1 (caar *dragonlist*))(+ 1 (cadar *dragonlist*))))
           (equal state (make-state (+ 1 (caar *dragonlist*))(- (cadar *dragonlist*) 1)))
           (equal state (make-state (- (caar *dragonlist*) 1)(+ 1 (cadar *dragonlist*))))
           (equal state (make-state (- (caar *dragonlist*) 1)(- (cadar *dragonlist*) 1)))) nil)
        (t (safeFromDragons state (cdr *dragonlist*)))
        ))


(defun safe (state)
    (cond
        ((equal (safeFromDragons state *dragonlist*) nil) nil)
        ((or (> (car state) 4)(> (cadr state) 4)(< (car state) 0)(< (cadr state) 0)) nil)
        (t state)
        )
    )

(defun gore (state)
    (safe (make-state (+ (car state) 1)(cadr state)))
    )

(defun dolu (state)
    (safe (make-state (- (car state) 1)(cadr state)))
    )

(defun levo (state)
    (safe (make-state (car state)(- (cadr state) 1)))
    )

(defun desno (state)
    (safe (make-state (car state)(+ (cadr state) 1)))
    )

(defun gorelevo (state)
    (safe(make-state (+ 1 (car state))(- (cadr state) 1)))
    )
(defun goredesno (state)
    (safe (make-state (+ 1 (car state))(+ 1 (cadr state))))
    )

(defun dolulevo (state)
    (safe (make-state (- (car state) 1)(- (cadr state) 1)))
    )
(defun doludesno (state)
    (safe (make-state (- (car state) 1)(+ (cadr state) 1)))
    )


(print (run-breadth *prince* *queen* '(gore dolu levo desno gorelevo goredesno dolulevo doludesno)))