The sieve of Sundaram: Difference between revisions
→{{header|Ruby}}: Add Ruby
(→{{header|Ruby}}: Add Ruby) |
|||
Line 1,262:
</pre>
=={{header|Ruby}}==
Based on the Python code from the Wikipedia lemma.
<lang ruby>def sieve_of_sundaram(upto)
n = (2.4 * upto * Math.log(upto)) / 2
k = (n - 3) / 2 + 1
bools = [true] * k
(0..(Integer.sqrt(n) - 3) / 2 + 1).each do |i|
p = 2*i + 3
s = (p*p - 3) / 2
(s..k).step(p){|j| bools[j] = false}
end
bools.filter_map.each_with_index {|b, i| (i + 1) * 2 + 1 if b }
end
p sieve_of_sundaram(100)
n = 1_000_000
puts "\nThe #{n}th sundaram prime is #{sieve_of_sundaram(n)[n-1]}"
</lang>
{{out}}
<pre>[3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541, 547]
The 1000000th sundaram prime is 15485867
</pre>
=={{header|Wren}}==
{{libheader|Wren-fmt}}
| |||