Equal prime and composite sums: Difference between revisions
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93952013 4555 12820
89171409882 118784 403340</syntaxhighlight>
=={{header|Java}}==
<syntaxhighlight lang="java">
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;
}
}
</syntaxhighlight>
{{ out }}
<pre>
Sum | Prime Index | Composite Index
----------------------------------------------
10 | 3 | 2
1988 | 33 | 51
14697 | 80 | 147
83292 | 175 | 361
1503397 | 660 | 1582
18859052 | 2143 | 5699
93952013 | 4556 | 12821
89171409882 | 118785 | 403341
</pre>
=={{header|jq}}==
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