Primes with digits in nondecreasing order: Difference between revisions
Primes with digits in nondecreasing order (view source)
Revision as of 08:10, 15 August 2021
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<pre>
2 3 5 7 11 13 17 19 23 29 37 47 59 67 79 89 113 127 137 139 149 157 167 179 199 223 227 229 233 239 257 269 277 337 347 349 359 367 379 389 449 457 467 479 499 557 569 577 599 677
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=={{header|Sidef}}==
Simple solution:
<lang ruby>say 1000.primes.grep { .digits.cons(2).all { .head >= .tail } }</lang>
Generate such primes from digits (asymptotically faster):
<lang ruby>func primes_with_nondecreasing_digits(upto, base = 10) {
upto = prev_prime(upto+1)
var list = []
var digits = @(1..^base -> flip)
var end_digits = digits.grep { .is_coprime(base) }
list << digits.grep { .is_prime && !.is_coprime(base) }...
for k in (0 .. upto.ilog(base)) {
digits.combinations_with_repetition(k, {|*a|
var v = a.digits2num(base)
next if (v*base + end_digits.tail > upto)
end_digits.each {|d|
var n = (v*base + d)
next if ((n >= base) && (a[0] > d))
list << n if n.is_prime
}
})
}
list.sort
}
say primes_with_nondecreasing_digits(1000)</lang>
{{out}}
<pre>
[2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 37, 47, 59, 67, 79, 89, 113, 127, 137, 139, 149, 157, 167, 179, 199, 223, 227, 229, 233, 239, 257, 269, 277, 337, 347, 349, 359, 367, 379, 389, 449, 457, 467, 479, 499, 557, 569, 577, 599, 677]
</pre>
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