Data update

Task/Equal-prime-and-composite-sums/Java/equal-prime-and-composite-sums.java

@@ -0,0 +1,106 @@
+import java.util.BitSet;
+import java.util.Objects;
+
+public final class EqualPrimeAndCompositeSums {
+
+	public static void main(String[] aArgs) {		
+	    PrimeIterator primeIterator = new PrimeIterator();
+	    CompositeIterator compositeIterator = new CompositeIterator();
+	    long primeSum = primeIterator.next();
+	    long compositeSum = compositeIterator.next();
+	    int primeIndex = 1;
+	    int compositeIndex = 1;
+	
+	    System.out.println("Sum           | Prime Index  | Composite Index");
+	    System.out.println("----------------------------------------------");
+	    int count = 0;
+	    while ( count < 8 ) {
+	        if ( primeSum == compositeSum ) {
+	        	System.out.println(String.format("%13d%s%12d%s%15d",
+	        		primeSum, " | ", primeIndex, " | ", compositeIndex));
+	        	
+	        	primeSum += primeIterator.next();
+	            primeIndex += 1;	
+	            compositeSum += compositeIterator.next();
+	            compositeIndex += 1;	
+	            count += 1;
+	        } else if ( primeSum < compositeSum ) {
+	            primeSum += primeIterator.next();
+	            primeIndex += 1;
+	        } else {
+	            compositeSum += compositeIterator.next();
+	            compositeIndex += 1;
+	        }
+	    }
+	}	
+	
+	private static class CompositeIterator {
+		
+		public CompositeIterator() {
+			primeIterator = new PrimeIterator();
+			prime = primeIterator.next();
+			composite = prime;
+			while ( composite == prime ) {
+				prime = primeIterator.next();
+				composite += 1;
+			}
+		}
+		
+		public int next() {
+		    final int result = composite;
+		    while ( ++composite == prime ) {
+		        prime = primeIterator.next();
+		    }
+		    return result;
+		}
+		
+		public int prime, composite;
+		private PrimeIterator primeIterator;
+		
+	}
+	
+	private static class PrimeIterator {
+		
+		public PrimeIterator() {
+			if ( Objects.isNull(sieve) ) {
+				listPrimeNumbers(10_000_000);
+			}			
+		}
+		
+		public int next() {
+			if ( lastPrime < sieve.cardinality() ) {
+				lastPrime = sieve.nextSetBit(lastPrime + 1);
+			} else {
+				do {
+					lastPrime += 2;
+				}
+				while ( ! isPrime(lastPrime) );				
+			}			
+			return lastPrime;
+		}
+		
+		private static boolean isPrime(int aCandidate) {
+			for ( int i = 2; i <= Math.sqrt(aCandidate); i = sieve.nextSetBit(i + 1) ) {
+				if ( aCandidate % i == 0 ) {
+					return false;
+				}
+			}
+			return true;
+		}
+		
+		private static void listPrimeNumbers(int aN) {
+			sieve = new BitSet(aN + 1);
+			sieve.set(2, aN + 1);
+			for ( int i = 2; i <= Math.sqrt(aN); i = sieve.nextSetBit(i + 1) ) {
+				for ( int j = i * i; j <= aN; j = j + i ) {
+					sieve.clear(j);
+				}
+			}
+		}
+		
+		private int lastPrime;
+		private static BitSet sieve;		
+		
+	}	
+
+}