38 lines
1.2 KiB
Common Lisp
38 lines
1.2 KiB
Common Lisp
;;;; Quick Find Algorithm
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;;;; This algorithm solve dynamic connectivity
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;;;; problem by providing a way to find if there
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;;;; is a path between two nodes in a dynamic graph
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(in-package :com.lisp-algo.union-find)
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;;; Base functions
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(defun qf-create-network (n)
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"Build a quick-find network using a dynamic vector"
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(let ((nodes (make-array n :fill-pointer 0)))
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(dotimes (id n)
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(vector-push id nodes))
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nodes))
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;; Link two nodes in the network
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(defun qf-union (network n1 n2)
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"Link two nodes in the quick-find network. union_ represent the union operation of the Quick Find Algorithm"
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(let ((v-n1 (elt network n1))
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(v-n2 (elt network n2))
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(new-network (copy-seq network)))
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(dotimes (n (length new-network))
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(if (= (elt new-network n) v-n2) (setf (elt new-network n) v-n1)))
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new-network))
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;;; Macro definitions
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(defmacro qf-connected (network n1 n2)
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" Return t if there is a path between n1 and n2, nil otherwise. connected represent the find operation of the Quick Find Algorithm"
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`(= (elt ,network ,n1) (elt ,network ,n2)))
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(defmacro qf-nunion (network n1 n2)
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"A destructive version of union_"
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`(setq ,network (union ,network ,n1 ,n2)))
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