27 lines
385 B
C++
27 lines
385 B
C++
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#include <math.h>
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int is_prime(unsigned n)
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{
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if (n <= 3)
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return 1;
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if (!(n & 1))
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return 0;
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if (n % 3 == 0)
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return 0;
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unsigned lim = unsigned(sqrt((double)n));
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unsigned d = 5;
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for (;;) {
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if (d > lim)
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break;
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if (n % d == 0)
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return 0;
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d += 2;
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if (d > lim)
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break;
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if (n % d == 0)
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return 0;
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d += 4;
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}
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return 1;
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}
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