64 lines
1.8 KiB
Racket
64 lines
1.8 KiB
Racket
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#lang racket
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(module+ test
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(require rackunit))
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(define (count-odds lst)
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(cond
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[(empty? lst) 0]
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[(odd? (first lst)) (add1 (count-odds (rest lst)))]
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[else (count-odds (rest lst))]))
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(module+ test
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(check-equal? (count-odds (list 3 2 1 1 2 3 4 5 5 6)) 6))
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(define (count-odds2 lst)
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(define (helper lst odds)
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(cond
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[(empty? lst) odds]
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[(odd? (first lst)) (helper (rest lst) (add1 odds))]
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[else (helper (rest lst) odds)]))
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(helper lst 0))
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(module+ test
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(check-equal? (count-odds2 (list 3 2 1 1 2 3 4 5 5 6)) 6)
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(define random-list (build-list 100 (lambda (x) (random 1 100))))
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(check-equal? (count-odds random-list) (count-odds2 random-list)))
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(define (count-odds3 lst)
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(for/fold
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([odds 0])
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([n lst])
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(cond
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[(odd? n) (add1 odds)]
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[else odds])))
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(module+ test
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(check-equal? (count-odds3 (list 3 2 1 1 2 3 4 5 5 6)) 6)
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(check-equal? (count-odds random-list) (count-odds3 random-list))
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(check-equal? (count-odds3 (list 3 2 1 1 2 3 4 5 5 6)) 6))
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(define big-list (range 50000000))
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(for* ([fun (list count-odds count-odds2 count-odds3)]
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[rep '(1 2 3)])
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(printf "~a ~a\n" fun rep)
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(time (fun big-list)))
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;#<procedure:count-odds> 1
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;cpu time: 22109 real time: 22390 gc time: 15828
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;#<procedure:count-odds> 2
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;cpu time: 19578 real time: 19679 gc time: 16250
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;#<procedure:count-odds> 3
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;cpu time: 18109 real time: 18231 gc time: 14859
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;#<procedure:count-odds2> 1
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;cpu time: 3125 real time: 3178 gc time: 93
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;#<procedure:count-odds2> 2
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;cpu time: 2765 real time: 2822 gc time: 31
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;#<procedure:count-odds2> 3
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;cpu time: 2765 real time: 2798 gc time: 31
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;#<procedure:count-odds3> 1
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;cpu time: 1000 real time: 1002 gc time: 0
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;#<procedure:count-odds3> 2
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;cpu time: 1187 real time: 1252 gc time: 15
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;#<procedure:count-odds3> 3
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;cpu time: 984 real time: 1002 gc time: 0
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