33 lines
1.1 KiB
Text
33 lines
1.1 KiB
Text
fun primesHM(): Sequence<Int> = sequence {
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yield(2)
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fun oddprms(): Sequence<Int> = sequence {
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yield(3); yield(5) // need at least 2 for initialization
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val hm = HashMap<Int,Int>()
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hm.put(9, 6)
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val bps = oddprms().iterator(); bps.next(); bps.next() // skip past 5
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yieldAll(generateSequence(SieveState(7, 5, 25)) {
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ss ->
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var n = ss.n; var q = ss.q
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n += 2
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while ( n >= q || hm.containsKey(n)) {
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if (n >= q) {
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val inc = ss.bp shl 1
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hm.put(n + inc, inc)
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val bp = bps.next(); ss.bp = bp; q = bp * bp
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}
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else {
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val inc = hm.remove(n)!!
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var next = n + inc
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while (hm.containsKey(next)) {
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next += inc
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}
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hm.put(next, inc)
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}
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n += 2
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}
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ss.n = n; ss.q = q
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ss
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}.map { it.n })
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}
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yieldAll(oddprms())
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}
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