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36 lines
1.2 KiB
Racket
36 lines
1.2 KiB
Racket
10 years ago
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#lang typed/racket/base
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(require (for-syntax racket/base racket/syntax))
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(require racket/list sugar/debug rackunit racket/function racket/vector sugar/cache "logger-typed.rkt")
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(define-logger ocm)
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#|
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Totally monotone matrix searching algorithms.
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The offline algorithm in ConcaveMinima is from Agarwal, Klawe, Moran,
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Shor, and Wilbur, Geometric applications of a matrix searching algorithm,
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Algorithmica 2, pp. 195-208 (1987).
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The online algorithm in OnlineConcaveMinima is from Galil and Park,
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A linear time algorithm for concave one-dimensional dynamic programming,
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manuscript, 1989, which simplifies earlier work on the same problem
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by Wilbur (J. Algorithms 1988) and Eppstein (J. Algorithms 1990).
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D. Eppstein, March 2002, significantly revised August 2005
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|#
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;(provide smawky? make-ocm reduce reduce2 (prefix-out ocm- (combine-out min-value min-index)))
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(define (select-elements xs is)
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(map (curry list-ref xs) is))
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(define (odd-elements xs)
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(select-elements xs (range 1 (length xs) 2)))
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(define (vector-odd-elements xs)
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(for/vector ([i (in-range (vector-length xs))] #:when (odd? i))
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(vector-ref xs i)))
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(define (even-elements xs)
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(select-elements xs (range 0 (length xs) 2)))
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