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Ludic numbers: Difference between revisions
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=={{header|Java}}==
{{works with|Java|1.5+}}
This example uses pre-calculated ranges for the first and third task items (noted in comments).
<lang java5>import java.util.ArrayList;
import java.util.List;
public class Ludic{
public static List<Integer> ludicUpTo(int n){
List<Integer> ludics = new ArrayList<Integer>(n);
for(int i = 1; i <= n; i++){ //fill the initial list
ludics.add(i);
}
//start at index 1 because the first ludic number is 1 and we don't remove anything for it
for(int cursor = 1; cursor < ludics.size(); cursor++){
int thisLudic = ludics.get(cursor); //the first item in the list is a ludic number
int removeCursor = cursor + thisLudic; //start removing that many items later
while(removeCursor < ludics.size()){
ludics.remove(removeCursor); //remove the next item
removeCursor = removeCursor + thisLudic - 1; //move the removal cursor up as many spaces as we need to
//then back one to make up for the item we just removed
}
}
return ludics;
}
public static List<List<Integer>> getTriplets(List<Integer> ludics){
List<List<Integer>> triplets = new ArrayList<List<Integer>>();
for(int i = 0; i < ludics.size() - 2; i++){ //only need to check up to the third to last item
int thisLudic = ludics.get(i);
if(ludics.contains(thisLudic + 2) && ludics.contains(thisLudic + 6)){
List<Integer> triplet = new ArrayList<Integer>(3);
triplet.add(thisLudic);
triplet.add(thisLudic + 2);
triplet.add(thisLudic + 6);
triplets.add(triplet);
}
}
return triplets;
}
public static void main(String[] srgs){
System.out.println("First 25 Ludics: " + ludicUpTo(110)); //110 will get us 25 numbers
System.out.println("Ludics up to 1000: " + ludicUpTo(1000).size());
System.out.println("2000th - 2005th Ludics: " + ludicUpTo(22000).subList(1999, 2005)); //22000 will get us 2005 numbers
System.out.println("Triplets up to 250: " + getTriplets(ludicUpTo(250)));
}
}</lang>
{{out}}
<pre>First 25 Ludics: [1, 2, 3, 5, 7, 11, 13, 17, 23, 25, 29, 37, 41, 43, 47, 53, 61, 67, 71, 77, 83, 89, 91, 97, 107]
Ludics up to 1000: 142
2000th - 2005th Ludics: [21475, 21481, 21487, 21493, 21503, 21511]
Triplets up to 250: [[1, 3, 7], [5, 7, 11], [11, 13, 17], [23, 25, 29], [41, 43, 47], [173, 175, 179], [221, 223, 227], [233, 235, 239]]</pre>
=={{header|Perl 6}}==
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