Euler 35

gistfile1.txt

#!/usr/local/bin/node

// first, prep prime seive up to 1MM

n=1000000;
myPrimes = new Array();
for (i=2;i<=n;i++)
	{
	myPrimes[i]=true;
	}
for (i=2;i<=n;i++)
	{
	if (myPrimes[i])
		{
		for (j=2*i;j<=n;j+=i)
			{
			myPrimes[j]=false;
			}
		}	
	}
	
// then check if each prime is circular
// if it is, add it to the de-duping array (circularsieve)

circularsieve = [];
for (i=0;i<=1000000;i++)
	{
	if (myPrimes[i])
		{
		carousel = i.toString();
		test = [];
		for (j=0;j<=carousel.length-1;j++)
			{
			copy = carousel; 
			a = carousel.slice(0,1);
			b = carousel.slice(1);
			carousel = b + a;
			if(myPrimes[Number(carousel)]!=true)
				{
				break;
				}
			if(myPrimes[Number(carousel)]==true && j==carousel.length-1)
				{
				circularsieve[Number(copy)] = true;
				}
			}		
		}
	}

// count up all the circular primes in the de-duping array

count = 0;
for (k=0;k<=circularsieve.length;k++)
	{
	if (circularsieve[k])
		{
//		console.log(k,"is a circular prime");
		count += 1;
		}
	}

console.log("total count is", count);