Sieve of Eratosthenes - Jason

gistfile1.cfm

<!--- Create array of all numbers --->
<cfset aNumbers = [] />

<!--- Initialize Array with unmarked, except one --->
<cfset arraySet(aNumbers, 2, 1000, "unmarked") />
<cfset aNumbers[1] = "one" />

<!--- Loop over Array --->
<cfloop from="2" to="#arrayLen(aNumbers)#" index="numIndex">

	<!--- If number is already marked, skip it --->
	<cfif aNumbers[numIndex] EQ "marked" OR aNumbers[numIndex] EQ "composite">
		<cfcontinue />
	</cfif>

	<!--- If we made it here, number is prime, mark it --->
	<cfset aNumbers[numIndex] = "marked" />

	<!--- Square the current index to go find multiples of the current prime to mark them --->
	<cfset nextNum = numIndex * numIndex />

	<!--- Go mark the multiples of the current prime by starting with its square and stepping by the current prime --->
	<cfloop from="#nextNum#" to="#arrayLen(aNumbers)#" step="#numIndex#" index="multipleIndex">
		<cfset aNumbers[multipleIndex] = "composite" />
	</cfloop>
</cfloop>

<style>
	td {
		margin:0; 
		padding: 0;
		width: 20px;
		height: 20px;
		padding: 10px;
	}

	.marked {
		background-color: green;
	}

	.composite {
		background-color: red;
	}

	.one {
		background-color: black;
	}
</style>

<cfoutput>
<table>
	<tr>
	<cfloop from="1" to="#arrayLen(aNumbers)#" index="tableIndex">
		<td class="#aNumbers[tableIndex]#">#tableIndex#</td>
		<cfif tableIndex MOD 10 EQ 0>
			</tr>
			<tr>
		</cfif>
	</cfloop>
	</tr>
</table>
</cfoutput>