118 lines
3.1 KiB
Kotlin
118 lines
3.1 KiB
Kotlin
import java.math.BigInteger
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val SMALL_PRIMES = listOf(
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2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97,
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101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199,
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211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293,
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307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397,
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401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499,
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503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599,
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601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691,
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701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797,
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809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887,
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907, 911, 919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997
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)
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fun isPrime(n: BigInteger): Boolean {
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if (n < 2.toBigInteger()) {
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return false
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}
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for (sp in SMALL_PRIMES) {
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val spb = sp.toBigInteger()
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if (n == spb) {
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return true
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}
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if (n % spb == BigInteger.ZERO) {
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return false
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}
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if (n < spb * spb) {
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//if (n > SMALL_PRIMES.last().toBigInteger()) {
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// println("Next: $n")
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//}
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return true
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}
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}
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return n.isProbablePrime(10)
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}
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fun cycle(n: BigInteger): BigInteger {
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var m = n
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var p = 1
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while (m >= BigInteger.TEN) {
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p *= 10
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m /= BigInteger.TEN
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}
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return m + BigInteger.TEN * (n % p.toBigInteger())
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}
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fun isCircularPrime(p: BigInteger): Boolean {
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if (!isPrime(p)) {
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return false
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}
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var p2 = cycle(p)
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while (p2 != p) {
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if (p2 < p || !isPrime(p2)) {
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return false
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}
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p2 = cycle(p2)
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}
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return true
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}
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fun testRepUnit(digits: Int) {
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var repUnit = BigInteger.ONE
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var count = digits - 1
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while (count > 0) {
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repUnit = BigInteger.TEN * repUnit + BigInteger.ONE
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count--
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}
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if (isPrime(repUnit)) {
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println("R($digits) is probably prime.")
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} else {
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println("R($digits) is not prime.")
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}
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}
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fun main() {
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println("First 19 circular primes:")
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var p = 2
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var count = 0
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while (count < 19) {
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if (isCircularPrime(p.toBigInteger())) {
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if (count > 0) {
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print(", ")
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}
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print(p)
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count++
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}
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p++
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}
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println()
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println("Next 4 circular primes:")
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var repUnit = BigInteger.ONE
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var digits = 1
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count = 0
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while (repUnit < p.toBigInteger()) {
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repUnit = BigInteger.TEN * repUnit + BigInteger.ONE
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digits++
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}
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while (count < 4) {
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if (isPrime(repUnit)) {
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print("R($digits) ")
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count++
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}
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repUnit = BigInteger.TEN * repUnit + BigInteger.ONE
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digits++
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}
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println()
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testRepUnit(5003)
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testRepUnit(9887)
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testRepUnit(15073)
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testRepUnit(25031)
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testRepUnit(35317)
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testRepUnit(49081)
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}
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