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// Fig. 21.40: fig21_40.cpp
// Using a bitset to demonstrate the Sieve of Eratosthenes.
#include <iostream>
using std::cin;
using std::cout;
using std::endl;
#include <iomanip>
using std::setw;
#include <bitset> // bitset class definition
#include <cmath> // sqrt prototype
int main()
{
const int size = 1024;
int value;
std::bitset< size > sieve;
sieve.flip();
// perform Sieve of Eratosthenes
int finalBit = sqrt( sieve.size() ) + 1;
for ( int i = 2; i < finalBit; ++i )
if ( sieve.test( i ) )
for ( int j = 2 * i; j < size; j += i )
sieve.reset( j );
cout << "The prime numbers in the range 2 to 1023 are:\n";
// display prime numbers in range 2-1023
for ( int k = 2, counter = 0; k < size; ++k )
if ( sieve.test( k ) ) {
cout << setw( 5 ) << k;
if ( ++counter % 12 == 0 )
cout << '\n';
} // end outer if
cout << endl;
// get value from user to determine whether value is prime
cout << "\nEnter a value from 1 to 1023 (-1 to end): ";
cin >> value;
while ( value != -1 ) {
if ( sieve[ value ] )
cout << value << " is a prime number\n";
else
cout << value << " is not a prime number\n";
cout << "\nEnter a value from 2 to 1023 (-1 to end): ";
cin >> value;
} // end while
return 0;
} // end main
/**************************************************************************
* (C) Copyright 1992-2003 by Deitel & Associates, Inc. and Prentice *
* Hall. All Rights Reserved. *
* *
* DISCLAIMER: The authors and publisher of this book have used their *
* best efforts in preparing the book. These efforts include the *
* development, research, and testing of the theories and programs *
* to determine their effectiveness. The authors and publisher make *
* no warranty of any kind, expressed or implied, with regard to these *
* programs or to the documentation contained in these books. The authors *
* and publisher shall not be liable in any event for incidental or *
* consequential damages in connection with, or arising out of, the *
* furnishing, performance, or use of these programs. *
*************************************************************************/
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