gcd方法：欧几里得算法

/** * 第二章练习 2.16 * @param max * @param min * @return */
	public static long gcdd(long a, long b){
		long max=a>b?a:b;
		long min=a>b?b:a;
		if(max == 0|| min == 0) {//base case
			return max==0?min : max;
		}else if(max%2==0&&min%2==0) { 
			return 2*gcdd(max/2,min/2);
		}else if(max%2==0&&min%2==1) {
			return gcdd(max/2,min);
		}else if(max%2==1&&min%2==0) {
			return gcdd(max,min/2);
		}else {
			return gcdd((max+min)/2,(max-min)/2);
		} 
	}