This program is essentially identical to the C++ implementation, except for the framing and the I/O statements. C#, Java, C++ and C are quite difficult to distinguish from one another.
This program compiles and runs under Visual Studio 2005.
using System;
using System.Collections.Generic;
using System.Text;
//////////////////////////////////////////////////////////
// Name: Peter M. Maurer
// Program: Sieve of Eratosthenes
// Due: Never
// Language: C#
//////////////////////////////////////////////////////////
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
int[] Candidates = new int[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)
{
Console.Write(i);
Console.WriteLine(" is prime");
}
}
}
}
}