gray-code

import java.util.ArrayList;

/**
 * 
 * @author gentleKay
 * The gray code is a binary numeral system where two successive values differ in only one bit.
 * Given a non-negative integer n representing the total number of bits in the code,print the sequence of gray code. A gray code sequence must begin with 0.
 * For example,2]. Its gray code sequence is:
 * 		00 - 0
		01 - 1
		11 - 3
		10 - 2
 * Note:
 * For a given n,a gray code sequence is not uniquely defined.
 * For example,1]is also a valid gray code sequence according to the above definition.
 * For now,the judge is able to judge based on one instance of gray code sequence. Sorry about that.
 * 
 * 灰色代码是一个二进制数字系统，其中两个连续值仅在一个位上不同。
 * 给定一个非负整数n，表示代码中的位总数，打印灰色代码的序列。灰色代码序列必须以0开头。
 * 例如，给定n=2，返回[0,2]。其灰色代码序列为：
 *		00 - 0
		01 - 1
		11 - 3
		10 - 2
 * 注：
 * 对于给定的n，灰色代码序列不是唯一定义的。
 * 例如，根据上述定义，[0,1]也是有效的灰色代码序列。
 * 目前，法官能够根据一个灰色编码序列的实例进行判断。很抱歉。
 */

public class Main23 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		System.out.println(Main23.grayCode(2));
	}
	
	public static ArrayList<Integer> grayCode(int n) {
        ArrayList<Integer> array = new ArrayList<>();
        int num = 1 << n; 
        for (int i=0;i<num ;i++) {
        	array.add(i >> 1^i);  //格雷码,十进制转二进制    和  >> 运算优先级高于 ^
        }
        return array;
    }
}