Project Euler - Problem 4

euler.java

package euler;

import java.util.Comparator;
import java.util.PriorityQueue;

public class Pal {
	public static void main(String[] args) {
		System.out.println(isPalindrome(1221));
		System.out.println(isPalindrome(1234));

		System.out.println(isPalindrome(191));
		System.out.println(isPalindrome(123));
		
		
		PriorityQueue<Integer> p = new PriorityQueue<Integer>(new Comparator<Integer>() {

			@Override
			public int compare(Integer o1, Integer o2) {
				if (o1.intValue() == o2.intValue()) return 0;
				return (o1.intValue() < o2.intValue() ? 1 : -1);
			};
		});
		
		for (int i = 100; i < 1000; i++) {
			for (int j = 100; j < 1000; j++) {
				int n = i*j;
				if (isPalindrome(n)) {
					p.add(n);
				}
			}
		}
		System.out.println(p.peek());
	}

	public static boolean isPalindrome(int n) {
		String s = String.valueOf(n);
		for (int i = 0; i < s.length() / 2; i++) {
			if (s.charAt(i) != s.charAt(s.length() - i - 1)) return false;
    }
		return true;
	}
}