Data Update

Task/Consecutive-primes-with-ascending-or-descending-differences/Java/consecutive-primes-with-ascending-or-descending-differences.java

@@ -0,0 +1,86 @@
+import java.util.ArrayList;
+import java.util.BitSet;
+import java.util.List;
+
+public final class ConsecutivePrimes {
+
+	public static void main(String[] aArgs) {
+		final int limit = 1_000_000;
+		List<Integer> primes = listPrimeNumbers(limit);
+		
+		List<Integer> asc = new ArrayList<Integer>();
+		List<Integer> desc = new ArrayList<Integer>();
+		List<List<Integer>> maxAsc = new ArrayList<List<Integer>>();
+		List<List<Integer>> maxDesc = new ArrayList<List<Integer>>();
+	    int maxAscSize = 0;
+	    int maxDescSize = 0;
+	
+	    for ( int prime : primes ) {
+	   	    final int ascSize = asc.size();
+	        if ( ascSize > 1 && prime - asc.get(ascSize - 1) <= asc.get(ascSize - 1) - asc.get(ascSize - 2) ) {
+	            asc = new ArrayList<Integer>(asc.subList(ascSize - 1, asc.size()));
+	        }	
+	        asc.add(prime);
+	
+	        if ( asc.size() >= maxAscSize ) {
+	            if ( asc.size() > maxAscSize ) {
+	                maxAscSize = asc.size();
+	                maxAsc.clear();
+	            }
+	            maxAsc.add( new ArrayList<Integer>(asc) );
+	        }
+	
+	        final int descSize = desc.size();
+	        if ( descSize > 1 && prime - desc.get(descSize - 1) >= desc.get(descSize - 1) - desc.get(descSize - 2) ) {
+	            desc = new ArrayList<Integer>(desc.subList(descSize - 1, desc.size()));
+	        }
+	        desc.add(prime);
+	
+	        if ( desc.size() >= maxDescSize ) {
+	            if ( desc.size() > maxDescSize ) {
+	                maxDescSize = desc.size();
+	                maxDesc.clear();
+	            }
+	            maxDesc.add( new ArrayList<Integer>(desc) );
+	        }
+	    }
+	
+	    System.out.println("Longest run(s) of ascending prime gaps up to " + limit + ":");
+	    for ( List<Integer> list : maxAsc ) {
+	        displayResult(list);
+	    }
+	    System.out.println();
+	
+	    System.out.println("Longest run(s) of descending prime gaps up to " + limit + ":");
+	    for( List<Integer> list : maxDesc ) {
+	        displayResult(list);
+	    }
+	}
+	
+	private static List<Integer> listPrimeNumbers(int aLimit) {
+		BitSet sieve = new BitSet(aLimit + 1);
+		sieve.set(2, aLimit + 1);
+		for ( int i = 2; i <= Math.sqrt(aLimit); i = sieve.nextSetBit(i + 1) ) {
+			for ( int j = i * i; j <= aLimit; j = 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 void displayResult(List<Integer> aList) {
+		for ( int i = 0; i < aList.size(); i++ ) {
+	        if ( i > 0 ) {
+	            System.out.print(" (" + ( aList.get(i) - aList.get(i - 1) ) + ") ");
+	        }
+	        System.out.print(aList.get(i));
+	    }
+	    System.out.println();
+	}
+
+}