mirror of
https://github.com/correl/euler.git
synced 2024-11-23 19:19:53 +00:00
26 lines
717 B
Haskell
26 lines
717 B
Haskell
|
{- Find the 10001st prime.
|
||
|
|
|
||
|
|
By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is 13.
|
||
|
|
What is the 10001st prime number?
|
||
|
|
-}
|
||
|
|
|
||
|
|
import Text.Printf
|
||
|
|
|
||
|
|
is_prime :: (Integral a) => a -> Bool
|
||
|
|
is_prime n
|
||
|
|
| n == 1 = False
|
||
|
|
| n < 4 = True
|
||
|
|
| n `rem` 2 == 0 = False
|
||
|
|
| n < 9 = True
|
||
|
|
| n `rem` 3 == 0 = False
|
||
|
|
| otherwise = do
|
||
|
|
let f = sqrt (fromIntegral n)
|
||
|
|
let checkprime x = (n `rem` x == 0 || n `rem` (x + 2) == 0)
|
||
|
|
not (or (map checkprime (takeWhile (<= floor f) [5,11..])))
|
||
|
|
|
||
|
|
primes = filter is_prime (2:[3,5..])
|
||
|
|
|
||
|
|
main = do
|
||
|
|
printf " 6th prime: %d\n" (primes !! 5 :: Integer)
|
||
|
|
printf "10001th prime: %d\n" (primes !! 10000 :: Integer)
|