diff options
Diffstat (limited to 'racket/leetcode/lc-504-base7.rkt')
| -rw-r--r-- | racket/leetcode/lc-504-base7.rkt | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/racket/leetcode/lc-504-base7.rkt b/racket/leetcode/lc-504-base7.rkt new file mode 100644 index 0000000..3e75052 --- /dev/null +++ b/racket/leetcode/lc-504-base7.rkt @@ -0,0 +1,16 @@ +#lang racket + +(define/contract (convert-to-base7 num) + (-> exact-integer? string?) + (define (max-base-power n base [pow 1]) + (cond [(n . = . (expt base pow)) pow] + [(n . < . (expt base pow)) (sub1 pow)] + [else (max-base-power n base (add1 pow))])) + (define (add-next-digit n pow acc) + (cond [(= pow 0) (string-append acc (number->string n))] + [else (add-next-digit (remainder n (expt 7 pow)) + (sub1 pow) + (string-append acc + (number->string (quotient n (expt 7 pow)))))])) + (string-append (if (negative? num) "-" "") + (add-next-digit (abs num) (max-base-power (abs num) 7) "")))
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