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- #!/usr/bin/env chibi-scheme
- ;; Solution for Nines and Zeros
- ;; Given an integer n, find the smallest number consisting only of the
- ;; digits zero and nine that is divisible by n.
- ;; I am using a brute-force algorithm to start with
- ;; Example: 23 --> 990909
- (import (scheme base)
- (scheme write)
- (srfi 1))
- (define (number->digits n)
- (string->list (number->string n)))
- (define (only-9-0? n)
- (null? (delete #\0 (delete #\9 (number->digits n)))))
- (define (find-9-0-multiple n)
- (let loop ((i 1))
- (if (only-9-0? (* i n))
- (* i n)
- (loop (+ i 1)))))
- (display (find-9-0-multiple 23))
- (newline)
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