This is the first implementation of this set. Most of the other implementations were derived from this one by direct translation. (This wasn't always possible.)
C++, as the most widely used language for large-scale applications, needs no introduction. At one time C++ was an extension of the C language. C++ compilers would compile C++ into C, which was then compiled into the appropriate assembly code. The original name of C++ is "C with classes".
This program compiles and runs under Visual Studio 2005.
//////////////////////////////////////////////////////////
// Name: Peter M. Maurer
// Program: Sieve of Eratosthenes
// Due: Never
// Language: C++
//////////////////////////////////////////////////////////
#include <iostream>
using namespace std;
int main()
{
// define the sieve data structure
int Candidates[1000];
int i;
for (i=0 ; i<1000 ; i++)
{
// everything is potentially prime until proven otherwise
Candidates[i] = 1;
}
// Neither 1 nor 0 is prime, so flag them off
Candidates[0] = 0;
Candidates[1] = 0;
// start the sieve with the integer 0
i = 0;
while (i<1000)
{
// advance to the next un-crossed out number.
// this number must be a prime
while (i<1000 && Candidates[i] == 0)
{
i++;
}
// insure against running off the end of the data structure
if (i<1000)
{
// cross out all multiples of the prime, starting with 2*p.
int j;
for (j=2 ; j*i < 1000 ; j++)
{
Candidates[j*i] = 0;
}
// advance to the next candidate
i++;
}
}
// all uncrossed-out numbers are prime (and only those numbers)
// print all primes
for (i=0 ; i<1000 ; i++)
{
if (Candidates[i] != 0)
{
cout<<i<<" is prime\n";
}
}
return 0;
}