Composite numbers k with no single digit factors whose factors are all substrings of k: Difference between revisions
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</pre> |
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=={{header|Scala}}== |
=={{header|Scala}}== |
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for Scala3 |
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<syntaxhighlight lang="scala"> |
<syntaxhighlight lang="scala"> |
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def isComposite(num: Int): Boolean = { |
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val numStr = num.toString |
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def iter(n: Int, start: Int): Boolean = { |
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val limit = math.sqrt(n).floor.toInt |
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(start to limit).dropWhile(n % _ > 0).headOption match { |
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case Some(v) if v < 10 => false |
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case Some(v) => |
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if (v == start || numStr.contains(v.toString)) iter(n / v, v) |
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else false |
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case None => n < num && numStr.contains(n.toString) |
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} |
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} |
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iter(num, 2) |
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} |
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def composites = Iterator.from(121, 2).filter(isComposite(_)) |
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@main def main = { |
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val start = System.currentTimeMillis |
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composites.take(20) |
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.grouped(10) |
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.foreach(grp => println(grp.map("%8d".format(_)).mkString(" "))) |
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val time = System.currentTimeMillis - start |
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println(s"time elapsed: $time ms") |
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} |
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</syntaxhighlight> |
</syntaxhighlight> |
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