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DistinctPrimeFactors.java
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DistinctPrimeFactors.java
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package devjava;
import java.util.HashSet;
import java.util.Set;
public class DistinctPrimeFactors {
static boolean isPrime(int factor) {
int counter = 0;
for (int i = 1; i <= Math.sqrt(factor); i++) {
if (factor % i == 0) {
counter++;
}
if (counter >= 2) {
return false;
}
}
return true;
}
static Set<Integer> getDistinctPrimeFactors(int n, Set<Integer> factors) {
if (isPrime(n)) {
factors.add(n);
return factors;
} else {
for (int i = 2; i < (n / 2); i++) {
if (n % i == 0) {
factors.add(i);
factors.addAll(getDistinctPrimeFactors(n / i, factors));
break;
}
}
}
return factors;
}
public static void main(String[] args) {
for (int i = 5; i <= 1000000; i++) {
if (getDistinctPrimeFactors(i - 3, new HashSet<Integer>()).size()
+ getDistinctPrimeFactors(i - 2, new HashSet<Integer>()).size()
+ getDistinctPrimeFactors(i - 1, new HashSet<Integer>()).size()
+ getDistinctPrimeFactors(i, new HashSet<Integer>()).size() == 16) {
System.out.println((i - 3) + " / " + (i - 2) + " / " + (i - 1) + " / " + i);
}
}
}
}