Added Sieve of Eratosthenes implementations

src/main/java/mattrixwv/SieveOfEratosthenes.java

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+package mattrixwv;
+
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map;
+
+
+public class SieveOfEratosthenes implements Iterator<Long>{
+	long possiblePrime;
+	private Map<Long, ArrayList<Long>> dict;
+
+	public SieveOfEratosthenes(){
+		dict = new HashMap<Long, ArrayList<Long>>();
+		possiblePrime = 2;
+	}
+	@Override
+	public boolean hasNext(){
+		return true;
+	}
+	@Override
+	public Long next(){
+		long prime;
+		if(possiblePrime > 2){
+			//Loop until you find a prime number
+			for(;dict.containsKey(possiblePrime);possiblePrime += 2){
+				//Create the next entry for all entries in the map
+				for(long num : dict.get(possiblePrime)){
+					if(!dict.containsKey(possiblePrime + num + num)){
+						ArrayList<Long> tempArray = new ArrayList<Long>(Arrays.asList(num));
+						dict.put(possiblePrime + num + num, tempArray);
+					}
+					else{
+						dict.get(possiblePrime + num + num).add(num);
+					}
+				}
+				//Delete the current entry
+				dict.remove(possiblePrime);
+			}
+			//Save that the number is a prime
+			prime = possiblePrime;
+			//Add the next entry to the prime
+			if(!dict.containsKey(prime * 3)){
+				ArrayList<Long> tempArray = new ArrayList<Long>(Arrays.asList(prime));
+				dict.put(prime * 3, tempArray);
+			}
+			else{
+				dict.get(prime * 3).add(prime);
+			}
+			//Move on to the next possible prime
+			possiblePrime += 2;
+		}
+		else{
+			//Return 2 and move to 3
+			prime = possiblePrime++;
+		}
+		return prime;
+	}
+}

src/main/java/mattrixwv/SieveOfEratosthenesBig.java

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

src/test/java/mattrixwv/TestSieveOfEratosthenes.java

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+package mattrixwv;
+
+
+import static org.junit.Assert.assertEquals;
+
+import java.math.BigInteger;
+import java.util.ArrayList;
+import java.util.Arrays;
+
+import org.junit.Test;
+
+
+public class TestSieveOfEratosthenes{
+	@Test
+	public void testSieveOfEratosthenes(){
+		//Test 1
+		SieveOfEratosthenes sieve = new SieveOfEratosthenes();
+		ArrayList<Long> correctAnswer = new ArrayList<Long>(Arrays.asList(2L, 3L, 5L, 7L, 11L, 13L, 17L, 19L, 23L, 29L, 31L, 37L, 41L, 43L, 47L, 53L, 59L, 61L, 67L, 71L, 73L, 79L, 83L, 89L, 97L));
+		ArrayList<Long> answer = new ArrayList<Long>();
+		for(int cnt = 0;cnt < 25;++cnt){
+			long prime = sieve.next();
+			answer.add(prime);
+		}
+		assertEquals("SieveOfEratosthenes failed", correctAnswer, answer);
+	}
+	@Test
+	public void testSieveOfEratosthenesBig(){
+		//Test 1
+		SieveOfEratosthenesBig sieve = new SieveOfEratosthenesBig();
+		ArrayList<BigInteger> correctAnswer = new ArrayList<BigInteger>(Arrays.asList(BigInteger.valueOf(2), BigInteger.valueOf(3), BigInteger.valueOf(5), BigInteger.valueOf(7), BigInteger.valueOf(11), BigInteger.valueOf(13), BigInteger.valueOf(17), BigInteger.valueOf(19), BigInteger.valueOf(23), BigInteger.valueOf(29), BigInteger.valueOf(31), BigInteger.valueOf(37), BigInteger.valueOf(41), BigInteger.valueOf(43), BigInteger.valueOf(47), BigInteger.valueOf(53), BigInteger.valueOf(59), BigInteger.valueOf(61), BigInteger.valueOf(67), BigInteger.valueOf(71), BigInteger.valueOf(73), BigInteger.valueOf(79), BigInteger.valueOf(83), BigInteger.valueOf(89), BigInteger.valueOf(97)));
+		ArrayList<BigInteger> answer = new ArrayList<BigInteger>();
+		for(int cnt = 0;cnt < 25;++cnt){
+			BigInteger prime = sieve.next();
+			answer.add(prime);
+		}
+		assertEquals("SieveOfEratosthenesBig failed", correctAnswer, answer);
+	}
+}