65 lines
1.7 KiB
Java
65 lines
1.7 KiB
Java
package mattrixwv;
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import java.math.BigInteger;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.HashMap;
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import java.util.Iterator;
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import java.util.Map;
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public class SieveOfEratosthenesBig implements Iterator<BigInteger>{
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BigInteger possiblePrime;
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private Map<BigInteger, ArrayList<BigInteger>> dict;
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public SieveOfEratosthenesBig(){
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dict = new HashMap<BigInteger, ArrayList<BigInteger>>();
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possiblePrime = BigInteger.TWO;
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}
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@Override
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public boolean hasNext(){
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return true;
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}
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@Override
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public BigInteger next(){
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BigInteger prime;
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if(possiblePrime.compareTo(BigInteger.TWO) > 0){
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//Loop until you find a prime number
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for(;dict.containsKey(possiblePrime);possiblePrime = possiblePrime.add(BigInteger.TWO)){
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//Create the next entry for all entries in the map
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for(BigInteger num : dict.get(possiblePrime)){
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BigInteger loc = possiblePrime.add(num).add(num);
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if(!dict.containsKey(loc)){
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ArrayList<BigInteger> tempArray = new ArrayList<BigInteger>(Arrays.asList(num));
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dict.put(loc, tempArray);
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}
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else{
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dict.get(loc).add(num);
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}
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}
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//Delete the current entry
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dict.remove(possiblePrime);
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}
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//Save that the number is a prime
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prime = possiblePrime;
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BigInteger loc = prime.multiply(BigInteger.valueOf(3));
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if(!dict.containsKey(loc)){
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ArrayList<BigInteger> tempArray = new ArrayList<BigInteger>(Arrays.asList(prime));
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dict.put(loc, tempArray);
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}
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else{
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dict.get(loc).add(prime);
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}
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//Move on to the next possible prime
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possiblePrime = possiblePrime.add(BigInteger.TWO);
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}
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else{
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//Return 2 and move to 3
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prime = possiblePrime;
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possiblePrime = possiblePrime.add(BigInteger.ONE);
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}
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return prime;
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}
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}
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