Here's what I have so far:
http://scratch.mit.edu/projects/14460081/
I have been trying to make it work for a while now, but it seems to get hung up on perfect squares and maybe multiples of 5. I think it is because I am trying to use multiple if/else blocks instead of a while block (Scratch doesn't have these). I've always been able to find a workaround, but now I'm just confused. Any advice is greatly appreciated!
Need help creating a sieve of Eratosthenes in Scratch

 Posts: 3
 Joined: Wed Apr 29, 2015 3:31 pm
Re: Need help creating a sieve of Eratosthenes in Scratch
This was a working solution in C#, not Scratch, but may help wanderers.
Code: Select all
private static List<long> SieveOfEratosthenes()
{
List<long> PrimesFound = new List<long>();
PrimesFound.Add(2);
long SquareRoot = (long)Math.Sqrt(MAX_VALUE);
BitArray Eliminated = new BitArray(MAX_VALUE + 1);
for (long i = 3; i <= MAX_VALUE; i += 2)
{
if (Eliminated[i] != true)
{
PrimesFound.Add(i);
if (i < SquareRoot)
{
for (int j = i * i; j <= MAX_VALUE; j += 2 * i)
{
Eliminated[j] = true;
}
}
}
}
return PrimesFound;
}