Arthur Barraux
35 lines
761 B
Scheme
35 lines
761 B
Scheme
; Find the largest palindrome made from the product of two 3-digit numbers.
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; could be 6 digits
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; 10^3 = 1,000 possible palindromes
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; or 5 digits
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; 10^3 = 1,000 possible palindromes
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; 2,000 total
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(define (palindrome? n)
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(define (check i str)
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(if (> (* i 2) (string-length str))
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#t
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(if (eq? (string-ref str i)
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(string-ref str (- (string-length str) (+ i 1))))
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(check (+ i 1) str)
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#f)))
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(check 0 (number->string n)))
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(define nums '())
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(do ((i 100 (+ i 1)))
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((> i 999) 'done)
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(do ((j 100 (+ j 1)))
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((> j 999) 'done)
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(let ((n (* i j)))
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(if (>= n 100000)
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(if (palindrome? n)
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(push n nums)
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)))))
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(display (reduce max 0 nums))
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