Data commit

Task/Ruth-Aaron-numbers/Java/ruth-aaron-numbers.java

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+import java.util.ArrayList;
+import java.util.BitSet;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.List;
+
+public final class RuthAaronNumbers {
+	
+	public static void main(String[] aArgs) {		
+		System.out.println("The first 30 Ruth-Aaron numbers (factors):");
+	    firstRuthAaronNumbers(30, NumberType.FACTOR);
+	
+	    System.out.println("The first 30 Ruth-Aaron numbers (divisors):");
+	    firstRuthAaronNumbers(30, NumberType.DIVISOR);
+	
+	    System.out.println("First Ruth-Aaron triple (factors): " + firstRuthAaronTriple(NumberType.FACTOR));
+		System.out.println();
+	
+		System.out.println("First Ruth-Aaron triple (divisors): " + firstRuthAaronTriple(NumberType.DIVISOR));
+		System.out.println();		
+	}
+	
+	private enum NumberType { DIVISOR, FACTOR }
+	
+	private static void firstRuthAaronNumbers(int aCount, NumberType aNumberType) {
+		primeSumOne = 0;
+		primeSumTwo = 0;
+		
+		for ( int n = 2, count = 0; count < aCount; n++ ) {			
+	        primeSumTwo = switch ( aNumberType ) {
+	        	case DIVISOR -> primeDivisorSum(n);
+	        	case FACTOR -> primeFactorSum(n);
+	        };
+	
+	        if ( primeSumOne == primeSumTwo ) {
+	            count += 1;
+	            System.out.print(String.format("%6d", n - 1));
+	            if ( count == aCount / 2 ) {
+	            	System.out.println();
+	            }
+	        }
+	
+	        primeSumOne = primeSumTwo;
+	    }
+		
+		System.out.println();
+		System.out.println();
+	}
+	
+	private static int firstRuthAaronTriple(NumberType aNumberType) {
+		primeSumOne = 0;
+		primeSumTwo = 0;
+		primeSumThree = 0;
+		
+		int n = 2;
+		boolean found = false;
+		while ( ! found ) {
+			primeSumThree = switch ( aNumberType ) {
+				case DIVISOR -> primeDivisorSum(n);
+				case FACTOR -> primeFactorSum(n);
+			};
+			
+			if ( primeSumOne == primeSumTwo && primeSumTwo == primeSumThree ) {
+				found = true;
+			}
+			
+			n += 1;			
+			primeSumOne = primeSumTwo;
+			primeSumTwo = primeSumThree;			
+		}
+		
+		return n - 2;
+	}
+	
+	private static int primeDivisorSum(int aNumber) {
+		return primeSum(aNumber, new HashSet<Integer>());
+	}
+	
+	private static int primeFactorSum(int aNumber) {
+		return primeSum(aNumber, new ArrayList<Integer>());
+	}
+	
+	private static int primeSum(int aNumber, Collection<Integer> aCollection) {
+		Collection<Integer> values = aCollection;
+
+		for ( int i = 0, prime = 2; prime * prime <= aNumber; i++ ) {
+			while ( aNumber % prime == 0 ) {
+				aNumber /= prime;
+				values.add(prime);
+			}
+			prime = primes.get(i + 1);
+		}
+
+		if ( aNumber > 1 ) {
+			values.add(aNumber);
+		}
+		
+		return values.stream().reduce(0, ( l, r ) -> l + r );
+	}
+	
+	private static List<Integer> listPrimeNumbersUpTo(int aNumber) {
+		BitSet sieve = new BitSet(aNumber + 1);
+		sieve.set(2, aNumber + 1);
+		
+		final int squareRoot = (int) Math.sqrt(aNumber);
+		for ( int i = 2; i <= squareRoot; i = sieve.nextSetBit(i + 1) ) {
+			for ( int j = i * i; j <= aNumber; j += i ) {
+				sieve.clear(j);
+			}
+		}
+		
+		List<Integer> result = new ArrayList<Integer>(sieve.cardinality());
+		for ( int i = 2; i >= 0; i = sieve.nextSetBit(i + 1) ) {
+			result.add(i);
+		}
+		
+		return result;
+	}
+	
+	private static int primeSumOne, primeSumTwo, primeSumThree;
+	private static List<Integer> primes = listPrimeNumbersUpTo(50_000);
+
+}