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28 lines
617 B
D
28 lines
617 B
D
/* Eratosthenes Sieve prime number calculation. */
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import std.conv;
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import std.stdio;
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import std.range;
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void main(string[] args)
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{
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immutable max = (1 < args.length)
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? args[1].to!size_t
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: 0x4000;
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size_t count = 1; // we have 2.
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// flags[i] = isPrime(2 * i + 3)
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auto flags = new bool[(max - 1) / 2];
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flags[] = true;
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foreach (i; 0..flags.length)
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{
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if (!flags[i])
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continue;
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auto prime = i + i + 3;
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foreach (k; iota(i + prime, flags.length, prime))
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flags[k] = false;
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count++;
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}
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writefln("%d primes", count);
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}
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