18 lines
496 B
Racket
18 lines
496 B
Racket
#lang racket
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(define (longest-collatz n)
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(let
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((pivot (list 0 0)))
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(define (collatz lst)
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(if (equal? (car lst) 1)
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lst
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(if (even? (car lst))
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(collatz (cons (quotient (car lst) 2) lst))
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(collatz (cons (+ 1 (* 3 (car lst))) lst)))))
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(for ((i (range 1 n)))
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(if (>= (length (collatz (list i))) (second pivot))
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(set! pivot (list i (length (collatz (list i)))))
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0))
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pivot))
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(display (first (longest-collatz 1000000))) |