1 | ;;; -*- Mode: Lisp -*-
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2 | ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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3 | ;;;
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4 | ;;; Copyright (C) 1999, 2002, 2009, 2015 Marek Rychlik <rychlik@u.arizona.edu>
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5 | ;;;
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6 | ;;; This program is free software; you can redistribute it and/or modify
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7 | ;;; it under the terms of the GNU General Public License as published by
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8 | ;;; the Free Software Foundation; either version 2 of the License, or
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9 | ;;; (at your option) any later version.
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10 | ;;;
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11 | ;;; This program is distributed in the hope that it will be useful,
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12 | ;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 | ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 | ;;; GNU General Public License for more details.
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15 | ;;;
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16 | ;;; You should have received a copy of the GNU General Public License
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17 | ;;; along with this program; if not, write to the Free Software
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18 | ;;; Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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19 | ;;;
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20 | ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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21 |
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22 | ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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23 | ;;
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24 | ;; A conventional implementation of a heap
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25 | ;;
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26 | ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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27 |
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28 | (defpackage "HEAP"
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29 | (:use :cl)
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30 | (:export "+HEAP-ALLOCATION-SIZE+"
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31 | "MAKE-HEAP"
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32 | "HEAP-SIZE"
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33 | "HEAP-INSERT"
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34 | "HEAP-REMOVE"
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35 | "HEAP-EMPTY-P"
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36 | ))
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37 |
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38 | (in-package :heap)
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39 | (defparameter *heap-allocation-size* 16)
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40 |
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41 | (defun make-heap (&key (element-type 'fixnum))
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42 | (make-array *heap-allocation-size* :element-type element-type :fill-pointer 1
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43 | :adjustable t))
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44 |
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45 | (defun heap-size (a)
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46 | "The number of elements on the heap. Does not count dummy head."
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47 | (1- (fill-pointer a)))
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48 |
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49 | (defun heap-upheap (a k
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50 | &optional
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51 | (test #'<=)
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52 | &aux (v (aref a k)))
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53 | (declare (fixnum k))
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54 | (assert (< 0 k (fill-pointer a)))
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55 | (loop
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56 | (let ((parent (ash k -1)))
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57 | (when (zerop parent) (return))
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58 | (unless (funcall test (aref a parent) v)
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59 | (return))
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60 | (setf (aref a k) (aref a parent)
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61 | k parent)))
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62 | (setf (aref a k) v)
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63 | a)
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64 |
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65 |
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66 | (defun heap-insert (a item &optional (test #'<=))
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67 | (vector-push-extend item a)
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68 | (heap-upheap a (1- (fill-pointer a)) test))
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69 |
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70 | (defun heap-downheap (a k
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71 | &optional
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72 | (test #'<=)
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73 | &aux (v (aref a k)) (j 0) (n (fill-pointer a)))
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74 | (declare (fixnum k n j))
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75 | (loop
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76 | (unless (<= k (ash n -1))
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77 | (return))
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78 | (setf j (ash k 1))
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79 | (if (and (< j n) (not (funcall test (aref a (1+ j)) (aref a j))))
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80 | (incf j))
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81 | (when (funcall test (aref a j) v)
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82 | (return))
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83 | (setf (aref a k) (aref a j)
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84 | k j))
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85 | (setf (aref a k) v)
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86 | a)
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87 |
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88 | (defun heap-remove (a &optional (test #'<=) &aux (v (aref a 1)))
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89 | (when (<= (fill-pointer a) 1) (error "Empty queue."))
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90 | (setf (aref a 1) (vector-pop a))
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91 | (heap-downheap a 1 test)
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92 | (values v a))
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93 |
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94 | (defun heap-empty-p (a)
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95 | (<= (fill-pointer a) 1))
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