lisp-algo/union-find/quick-find.lisp

;;;; Quick Find Algorithm
;;;; This algorithm solve dynamic connectivity
;;;; problem by providing a way to find if there
;;;; is a path between two nodes in a dynamic graph

(in-package :com.lisp-algo.union-find)

(defclass quick-find ()
  ((nw-size
    :initarg :network-size
    :initform 10
    :accessor network-size)
   (nw
    :initform nil
    :accessor network)))

(defmethod initialize-instance :after ((algo quick-find) &key)
  ;; Initialize network using dynamic vector
  (let* ((nw-size (slot-value algo 'nw-size))
        (nodes (make-array nw-size :fill-pointer 0)))
    (dotimes (id nw-size)
      (vector-push id nodes))
    (setf (slot-value algo 'nw) nodes)))

(defmethod union ((algo-instance quick-find) n1 n2)
  (with-slots ((nw nw)) algo-instance
  (let ((v-n1 (elt nw n1))
        (v-n2 (elt nw n2))
        (new-network (copy-seq nw)))
    (dotimes (n (length new-network))
      (if (= (elt new-network n) v-n2) (setf (elt new-network n) v-n1)))
    (setf nw new-network))))

(defmethod connected ((algo-instance quick-find) n1 n2)
  " Return t if there is a path between n1 and n2, nil otherwise. connected represent the find operation of the Quick Find Algorithm"
  (with-slots ((nw nw)) algo-instance
    (= (elt nw n1) (elt nw n2))))