指针之6.6

/*
 * The changes needed to the problem are minor:Istead of printing rhe primes,they are counted.
 * 2010-11-20
 */

/*
 * Go through the entire sieve now and count how many primes there are
 * per thousand numbers.
 */

 

n_primes = 1;
limit = 1000;

for( bit_number = 0, number = 3;
    number <= MAX_VALUE;
    bit_number += 1, number += 2 )
{
        if( test_bit( sieve, bit_number ) )
        {
            printf( "%d-%d: %d\n", limit - 1000, limit, n_primes );
            n_primes = 0;
            limit += 1000;
        }
        if( test_bit( sieve, bit_number ) )
            n_primes += 1;
}
printf( "%d-%d: %d\n", limit - 1000, limit, n_primes );