ホーム - Project Euler

Problem 10¶

#!r6rs
#!chezscheme

(import (chezscheme))

(define answer-10
  (let ((table (make-vector 2000001 #t))
        (count (isqrt 2000000)))
    (vector-set! table 0 #f)
    (vector-set! table 1 #f)

    (let loop1 ((index 2))
      (cond
        [(< count index)
         (let loop2 ((index 0) (result 0))
           (cond
             [(< 2000000 index) result]
             [(vector-ref table index)
              (loop2 (add1 index) (+ result index))]
             [else (loop2 (add1 index) result)]))]
        [(vector-ref table index)
         (let loop3 ((current (* index 2)))
           (cond
             [(< 2000000 current)
              (loop1 (add1 index))]
             [else
               (vector-set! table current #f)
               (loop3 (+ current index))]))]
        [else (loop1 (add1 index))]))))

(printf "10: ~D~%" answer-10)