Ruth-Aaron numbers: Difference between revisions
→{{header|Java}}
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=={{header|Java}}==
<syntaxhighlight
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);
}
</syntaxhighlight>
{{ out }}
<pre>
The first 30 Ruth-Aaron numbers (factors):
5 8 15 77 125 714 948 1330 1520 1862 2491 3248 4185 4191 5405
5560 5959 6867 8280 8463 10647 12351 14587 16932 17080 18490 20450 24895 26642 26649
The first 30 Ruth-Aaron numbers (divisors):
5 24 49 77 104 153 369 492 714 1682 2107 2299 2600 2783 5405
6556 6811 8855 9800 12726 13775 18655 21183 24024 24432 24880 25839 26642 35456 40081
First Ruth-Aaron triple (factors): 417163
First Ruth-Aaron triple (divisors): 89460295
</pre>
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