Project Euler > Problem 85 > Counting rectangles (Java Solution)

Problem:

By counting carefully it can be seen that a rectangular grid measuring 3 by 2 contains eighteen rectangles:

Although there exists no rectangular grid that contains exactly two million rectangles, find the area of the grid with the nearest solution.


Solution:

55

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

public interface EulerSolution{

public String run();

}
/* 
* Solution to Project Euler problem 35
* By Nayuki Minase
*
* http://nayuki.eigenstate.org/page/project-euler-solutions
* https://github.com/nayuki/Project-Euler-solutions
*/


public final class p035 implements EulerSolution {

public static void main(String[] args) {
System.out.println(new p035().run());
}


private static final int LIMIT = Library.pow(10, 6);

private boolean[] isPrime = Library.listPrimality(LIMIT - 1);


public String run() {
int count = 0;
for (int i = 0; i < isPrime.length; i++) {
if (isCircularPrime(i))
count++;
}
return Integer.toString(count);
}


private boolean isCircularPrime(int n) {
String s = Integer.toString(n);
for (int i = 0; i < s.length(); i++) {
if (!isPrime[Integer.parseInt(s.substring(i) + s.substring(0, i))])
return false;
}
return true;
}

}


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