Honaker primes: Difference between revisions
Add Scala implementation
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(p:46 ,ind:826 ,val:6343) (p:47 ,ind:827 ,val:6353) (p:48 ,ind:847 ,val:6553)
(p:49 ,ind:848 ,val:6563) (p:50 ,ind:857 ,val:6653)</pre>
=={{header|Scala}}==
{{trans|Java}}
<syntaxhighlight lang="Scala">
import scala.collection.mutable.ListBuffer
object HonakerPrimes {
def main(args: Array[String]): Unit = {
sievePrimes(5000000)
println("The first 50 Honaker primes (honaker index: prime index, prime):")
for (i <- 1 to 50) {
print(f"${nextHonakerPrime()}%17s${if (i % 5 == 0) "\n" else " "}")
}
for (i <- 51 until 10000) {
nextHonakerPrime()
}
println()
println(s"The 10,000th Honaker prime is: ${nextHonakerPrime()}")
}
private def nextHonakerPrime(): HonakerPrime = {
honakerIndex += 1
primeIndex += 1
while (digitalSum(primeIndex) != digitalSum(primes(primeIndex - 1))) {
primeIndex += 1
}
HonakerPrime(honakerIndex, primeIndex, primes(primeIndex - 1))
}
private def digitalSum(number: Int): Int = {
number.toString.map(_.asDigit).sum
}
private def sievePrimes(limit: Int): Unit = {
primes += 2
val halfLimit = (limit + 1) / 2
val composite = Array.fill(halfLimit)(false)
var i = 1
var p = 3
while (i < halfLimit) {
if (!composite(i)) {
primes += p
var a = i + p
while (a < halfLimit) {
composite(a) = true
a += p
}
}
i += 1
p += 2
}
}
private var honakerIndex = 0
private var primeIndex = 0
private val primes = ListBuffer[Int]()
case class HonakerPrime(honakerIndex: Int, primeIndex: Int, prime: Int) {
override def toString: String = s"($honakerIndex: $primeIndex, $prime)"
}
}
</syntaxhighlight>
{{out}}
<pre>
The first 50 Honaker primes (honaker index: prime index, prime):
(1: 32, 131) (2: 56, 263) (3: 88, 457) (4: 175, 1039) (5: 176, 1049)
(6: 182, 1091) (7: 212, 1301) (8: 218, 1361) (9: 227, 1433) (10: 248, 1571)
(11: 293, 1913) (12: 295, 1933) (13: 323, 2141) (14: 331, 2221) (15: 338, 2273)
(16: 362, 2441) (17: 377, 2591) (18: 386, 2663) (19: 394, 2707) (20: 397, 2719)
(21: 398, 2729) (22: 409, 2803) (23: 439, 3067) (24: 446, 3137) (25: 457, 3229)
(26: 481, 3433) (27: 499, 3559) (28: 508, 3631) (29: 563, 4091) (30: 571, 4153)
(31: 595, 4357) (32: 599, 4397) (33: 635, 4703) (34: 637, 4723) (35: 655, 4903)
(36: 671, 5009) (37: 728, 5507) (38: 751, 5701) (39: 752, 5711) (40: 755, 5741)
(41: 761, 5801) (42: 767, 5843) (43: 779, 5927) (44: 820, 6301) (45: 821, 6311)
(46: 826, 6343) (47: 827, 6353) (48: 847, 6553) (49: 848, 6563) (50: 857, 6653)
The 10,000th Honaker prime is: (10000: 286069, 4043749)
</pre>
=={{header|Sidef}}==
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