Parallel calculations: Difference between revisions
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<pre> |
<pre> |
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The number that has the largest minimum prime factor is 98421229882942378967, with a smallest factor of 736717 |
The number that has the largest minimum prime factor is 98421229882942378967, with a smallest factor of 736717 |
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</pre> |
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=={{header|Kotlin}}== |
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<lang scala>// version 1.1.51 |
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import java.util.stream.Collectors |
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/* returns the number itself, its smallest prime factor and all its prime factors */ |
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fun primeFactorInfo(n: Int): Triple<Int, Int, List<Int>> { |
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if (n <= 1) throw IllegalArgumentException("Number must be more than one") |
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if (isPrime(n)) return Triple(n, n, listOf(n)) |
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val factors = mutableListOf<Int>() |
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var factor = 2 |
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var nn = n |
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while (true) { |
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if (nn % factor == 0) { |
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factors.add(factor) |
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nn /= factor |
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if (nn == 1) return Triple(n, factors.min()!!, factors) |
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if (isPrime(nn)) factor = nn |
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} |
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else if (factor >= 3) factor += 2 |
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else factor = 3 |
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} |
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} |
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fun isPrime(n: Int) : Boolean { |
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if (n < 2) return false |
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if (n % 2 == 0) return n == 2 |
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if (n % 3 == 0) return n == 3 |
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var d = 5 |
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while (d * d <= n) { |
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if (n % d == 0) return false |
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d += 2 |
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if (n % d == 0) return false |
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d += 4 |
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} |
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return true |
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} |
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fun main(args: Array<String>) { |
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val numbers = listOf( |
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12757923, 12878611, 12878893, 12757923, 15808973, 15780709, 197622519 |
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) |
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val info = numbers.stream() |
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.parallel() |
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.map { primeFactorInfo(it) } |
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.collect(Collectors.toList()) |
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val maxFactor = info.maxBy { it.second }!!.second |
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val results = info.filter { it.second == maxFactor } |
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println("The following number(s) have the largest minimal prime factor of $maxFactor:") |
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for (result in results) { |
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println(" ${result.first} whose prime factors are ${result.third}") |
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} |
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}</lang> |
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{{out}} |
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<pre> |
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The following number(s) have the largest minimal prime factor of 47: |
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12878611 whose prime factors are [47, 101, 2713] |
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12878893 whose prime factors are [47, 274019] |
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</pre> |
</pre> |
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