Problem 3 » 履歴 » リビジョン 3
リビジョン 2 (Noppi, 2023/12/27 04:44) → リビジョン 3/4 (Noppi, 2023/12/27 12:14)
[ホーム](https://redmine.noppi.jp) - [[Wiki|Project Euler]]
# [[Problem 3]]
## Largest Prime Factor
The prime factors of $13195$ are $5, 7, 13$ and $29$.
What is the largest prime factor of the number $600851475143$?
## 最大の素因数
13195 の素因数は 5, 7, 13, 29 である.
600851475143 の素因数のうち最大のものを求めよ.
```scheme
#!r6rs
#!chezscheme
(import (chezscheme))
(define answer-3
(let* ([n 600851475143]
[check-max (isqrt n)])
(let loop ([current 3] [rest n] [max-prime 1])
(cond
[(< check-max current) max-prime]
[(zero? (mod rest current))
(loop current (div rest current) current)]
[else (loop (+ current 2) rest max-prime)]))))
(printf "3: ~D~%" answer-3)
```