85 lines
2.1 KiB
C++
85 lines
2.1 KiB
C++
// Copyright (c) .NET Foundation. All rights reserved.
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// Licensed under the MIT License. See License.txt in the project root for license information.
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#pragma once
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#include <math.h>
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#include <stdlib.h>
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//
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// Pre-calculated prime numbers (up to 10,049,369).
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//
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extern __declspec(selectany) const DWORD g_Primes [] = {
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3, 7, 11, 17, 23, 29, 37, 47, 59, 71, 89, 107, 131, 163, 197, 239, 293, 353, 431, 521, 631,
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761, 919, 1103, 1327, 1597, 1931, 2333, 2801, 3371, 4049, 4861, 5839, 7013, 8419, 10103,
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12143, 14591, 17519, 21023, 25229, 30293, 36353, 43627, 52361, 62851, 75431, 90523, 108631,
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130363, 156437, 187751, 225307, 270371, 324449, 389357, 467237, 560689, 672827, 807403,
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968897, 1162687, 1395263, 1674319, 2009191, 2411033, 2893249, 3471899, 4166287, 4999559,
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5999471, 7199369, 7849369, 8649369, 9249369, 10049369
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};
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class PRIME
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{
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public:
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static
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DWORD
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GetPrime(
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DWORD dwMinimum
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)
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{
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//
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// Try to use the precalculated numbers.
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//
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for ( DWORD Index = 0; Index < _countof( g_Primes ); Index++ )
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{
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DWORD dwCandidate = g_Primes[Index];
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if ( dwCandidate >= dwMinimum )
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{
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return dwCandidate;
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}
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}
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//
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// Do calculation.
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//
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for ( DWORD dwCandidate = dwMinimum | 1;
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dwCandidate < MAXDWORD;
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dwCandidate += 2 )
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{
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if ( IsPrime( dwCandidate ) )
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{
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return dwCandidate;
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}
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}
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return dwMinimum;
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}
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private:
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static
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BOOL
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IsPrime(
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DWORD dwCandidate
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)
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{
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if ((dwCandidate & 1) == 0)
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{
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return ( dwCandidate == 2 );
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}
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DWORD dwMax = static_cast<DWORD>(sqrt(static_cast<double>(dwCandidate)));
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for ( DWORD Index = 3; Index <= dwMax; Index += 2 )
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{
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if ( (dwCandidate % Index) == 0 )
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{
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return FALSE;
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}
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}
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return TRUE;
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}
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PRIME() {}
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~PRIME() {}
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}; |