31 lines
1.1 KiB
Scheme
31 lines
1.1 KiB
Scheme
(load "util.scm")
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(define (val tree) (car tree))
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(define (children tree) (cdr tree))
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(define (new-tree val children)
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(let loop ((ls '()) (children children))
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(if (null? children) (cons val ls)
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(loop (append ls (new-tree (car children) '())) (cdr children)))))
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(define (tree val children)
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(new-tree val (map (lambda (x) (new-tree x '())) children)))
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(define (tree-step tree)
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(if (null? (children tree))
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(new-tree (val tree) (map (lambda (x) (new-tree x '())) (next (val tree))))
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(new-tree (val tree) (map tree-step (children tree)))))
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(define (longest-path tree)
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(cdr (let longest-path ((tree tree))
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(if (null? (children tree))
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(list (val tree))
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(cons (val tree)
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(fold (lambda (curr prev) (if (< (length prev) (length curr)) curr prev))
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'()
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(map longest-path (children tree))))))))
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; --- change this function to control behavior of tree ---
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(define (next val)
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(filter prime? (map (lambda (d) (+ (* val 10) d)) (range 10))))
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; (define (next val)
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; (filter prime? (map (lambda (d) (+ (* d (expt 10 (digits val))) val)) (cdr (range 10)))))
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