94 lines
2.3 KiB
Common Lisp
94 lines
2.3 KiB
Common Lisp
;; Path format: (start-point end-point previous-point distance)
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(setq path-list `(
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(a b ,nil 7)
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(a c ,nil 9)
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(a f ,nil 14)
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(b c ,nil 10)
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(b d ,nil 15)
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(c d ,nil 11)
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(c f ,nil 2)
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(d e ,nil 6)
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(e f ,nil 9)
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))
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(defun calculate-shortest-path ()
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(let ((shortest-path '())
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(head-point (nth 0 (nth 0 path-list))))
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(defun combine-new-path (path1 path2)
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(list (nth 0 path1) (nth 1 path2) (nth 0 path2)
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(+ (nth 3 path1) (nth 3 path2))) )
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(defun find-shortest-path (start end)
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(seq-find (lambda (item)
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(and (eq (nth 0 item) start) (eq (nth 1 item) end)))
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shortest-path)
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)
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(defun add-shortest-path (item)
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(add-to-list 'shortest-path item) )
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(defun process-path (path)
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(if (eq head-point (nth 0 path))
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(add-to-list 'shortest-path path)
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(progn
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(dolist (spath shortest-path)
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(when (eq (nth 1 spath) (nth 0 path))
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(let* ((new-path (combine-new-path spath path))
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(spath-found (find-shortest-path (nth 0 new-path)
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(nth 1 new-path))))
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(if spath-found
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(when (< (nth 3 new-path) (nth 3 spath-found))
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(setcdr (nthcdr 1 spath-found) (list (nth 2 new-path) (nth 3 new-path)))
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)
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(add-shortest-path new-path)) ) ) ) ) ) )
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(defun find-shortest-route (start end)
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(let ((point-list '())
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(end-point end)
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path-found)
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(add-to-list 'point-list end)
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(catch 'no-more-path
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(while 't
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(setq path-found (find-shortest-path start end-point))
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(if (or (not path-found) (not (nth 2 path-found)))
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(throw 'no-more-path nil)
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(progn
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(add-to-list 'point-list (nth 2 path-found))
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(setq end-point (nth 2 path-found)) )
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)
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)
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)
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(add-to-list 'point-list start)
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)
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)
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(defun show-shortest-path (start end)
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(let ((path-found (find-shortest-path start end))
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(route-found (find-shortest-route start end)))
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(if path-found
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(progn
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(message "shortest distance: %s" (nth 3 path-found))
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(message "shortest route: %s" route-found) )
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(message "shortest path not found") )
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)
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(message "--") )
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;; Process each path
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(dolist (path path-list)
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(process-path path) )
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(message "from %s to %s:" 'a 'e)
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(show-shortest-path 'a 'e)
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(message "from %s to %s:" 'a 'f)
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(show-shortest-path 'a 'f)
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)
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)
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(calculate-shortest-path)
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