aparler/RosettaCodeData
1
0
Fork 0
Code Issues 12 Pull requests 3 Projects Releases Packages Wiki Activity Actions

Data commit

Browse source
This commit is contained in:
Ingy döt Net 2023-07-01 11:58:00 -04:00
parent 7387c8f97b
commit cb5bb5e222
199093 changed files with 3378972 additions and 0 deletions
Download patch file Download diff file Expand all files Collapse all files

112
Task/Zumkeller-numbers/Java/zumkeller-numbers.java Normal file
View file

@ -0,0 +1,112 @@
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class ZumkellerNumbers {
public static void main(String[] args) {
int n = 1;
System.out.printf("First 220 Zumkeller numbers:%n");
for ( int count = 1 ; count <= 220 ; n += 1 ) {
if ( isZumkeller(n) ) {
System.out.printf("%3d ", n);
if ( count % 20 == 0 ) {
System.out.printf("%n");
}
count++;
}
}
n = 1;
System.out.printf("%nFirst 40 odd Zumkeller numbers:%n");
for ( int count = 1 ; count <= 40 ; n += 2 ) {
if ( isZumkeller(n) ) {
System.out.printf("%6d", n);
if ( count % 10 == 0 ) {
System.out.printf("%n");
}
count++;
}
}
n = 1;
System.out.printf("%nFirst 40 odd Zumkeller numbers that do not end in a 5:%n");
for ( int count = 1 ; count <= 40 ; n += 2 ) {
if ( n % 5 != 0 && isZumkeller(n) ) {
System.out.printf("%8d", n);
if ( count % 10 == 0 ) {
System.out.printf("%n");
}
count++;
}
}
}
private static boolean isZumkeller(int n) {
// numbers congruent to 6 or 12 modulo 18 are Zumkeller numbers
if ( n % 18 == 6 || n % 18 == 12 ) {
return true;
}
List<Integer> divisors = getDivisors(n);
int divisorSum = divisors.stream().mapToInt(i -> i.intValue()).sum();
// divisor sum cannot be odd
if ( divisorSum % 2 == 1 ) {
return false;
}
// numbers where n is odd and the abundance is even are Zumkeller numbers
int abundance = divisorSum - 2 * n;
if ( n % 2 == 1 && abundance > 0 && abundance % 2 == 0 ) {
return true;
}
Collections.sort(divisors);
int j = divisors.size() - 1;
int sum = divisorSum/2;
// Largest divisor larger than sum - then cannot partition and not Zumkeller number
if ( divisors.get(j) > sum ) {
return false;
}
return canPartition(j, divisors, sum, new int[2]);
}
private static boolean canPartition(int j, List<Integer> divisors, int sum, int[] buckets) {
if ( j < 0 ) {
return true;
}
for ( int i = 0 ; i < 2 ; i++ ) {
if ( buckets[i] + divisors.get(j) <= sum ) {
buckets[i] += divisors.get(j);
if ( canPartition(j-1, divisors, sum, buckets) ) {
return true;
}
buckets[i] -= divisors.get(j);
}
if( buckets[i] == 0 ) {
break;
}
}
return false;
}
private static final List<Integer> getDivisors(int number) {
List<Integer> divisors = new ArrayList<Integer>();
long sqrt = (long) Math.sqrt(number);
for ( int i = 1 ; i <= sqrt ; i++ ) {
if ( number % i == 0 ) {
divisors.add(i);
int div = number / i;
if ( div != i ) {
divisors.add(div);
}
}
}
return divisors;
}
}