求最大公约数----辗转相除法

一般写法：

public class Main {
	public static void main(String[] args) {
		System.out.println(gcd(18, 2));
	}

	private static int gcd(int a, int b) {
		// TODO Auto-generated method stub
		while (b != 0) {
			int c = a % b;
			a = b;
			b = c;
		}
		return a;
	}
}

递归实现

public class Main {
	public static void main(String[] args) {
		System.out.println(gcd(18, 2));
	}
	
	private static int gcd(int a, int b) {
		// TODO Auto-generated method stub
		if (b == 0) {
			return a;
		}
		return gcd(b, a%b);
	}
}