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48 lines
1.3 KiB
Racket
48 lines
1.3 KiB
Racket
3 years ago
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#lang racket
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(define test-data (list
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199
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200
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263
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))
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; part 1
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(define (sum data)
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(cdr
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(foldl (λ (el acc)
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(let ([prev (car acc)]
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[total (cdr acc)])
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(if (> el prev)
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(cons el (+ 1 total))
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(cons el total))))
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(cons (car data) 0)
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data)))
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(define part1 (sum test-data))
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; part 2
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; fold over the data
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; initial value will be a pair of 2 lists
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; first list is the original list, 2nd is the new sliding window
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(define sliding-window
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(reverse
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(cdr
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(foldl (λ (el acc)
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;(writeln acc) ; debug
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(let ([orig (car acc)] ; grab the rest of the original list from the accumulator
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[window (cdr acc)] ; grab the window list that we have so far
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[one (car (car acc))] ; first element of original list
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[two (car (rest (car acc)))]
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[three (car (rest (rest (car acc))))])
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(cons (rest orig) (cons (+ one two three) window)))) ; return a pair - first elem is the new window list. 2nd elem is the rest of the original list
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(cons (append test-data (list 0 0)) empty) ; start with an empty window list an the original list. add 2 0s at the end to cheat
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test-data))))
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(define part2 (sum sliding-window))
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