Project Euler > Problem 47 > Distinct primes factors (Java Solution)

Problem:

The first two consecutive numbers to have two distinct prime factors are:

14 = 2 [×] 7
15 = 3 [×] 5

The first three consecutive numbers to have three distinct prime factors are:

644 = 2² [×] 7 [×] 23
645 = 3 [×] 5 [×] 43
646 = 2 [×] 17 [×] 19.

Find the first four consecutive integers to have four distinct prime factors. What is the first of these numbers?

Solution:

134043

Code:
The solution may include methods that will be found here: Library.java .

public interface EulerSolution{

public String run();

}

/* 
 * Solution to Project Euler problem 47
 * By Nayuki Minase
 * 
 * http://nayuki.eigenstate.org/page/project-euler-solutions
 * https://github.com/nayuki/Project-Euler-solutions
 */


public final class p047 implements EulerSolution {
 
 public static void main(String[] args) {
  System.out.println(new p047().run());
 }
 
 
 public String run() {
  for (int i = 2; ; i++) {
   if (       has4PrimeFactors(i + 0)
           && has4PrimeFactors(i + 1)
           && has4PrimeFactors(i + 2)
           && has4PrimeFactors(i + 3))
    return Integer.toString(i);
  }
 }
 
 
 private static boolean has4PrimeFactors(int n) {
  return countDistinctPrimeFactors(n) == 4;
 }
 
 
 private static int countDistinctPrimeFactors(int n) {
  int count = 0;
  for (int i = 2, end = Library.sqrt(n); i <= end; i++) {
   if (n % i == 0) {
    do n /= i;
    while (n % i == 0);
    count++;
    end = Library.sqrt(n);
   }
  }
  if (n > 1)
   count++;
  return count;
 }
 
}