leetCode 89.Gray Code （格雷码） 解题思路和方法

标签：leetcode

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, given n = 2, return [0,1,3,2]. 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, [0,2,3,1] 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.

代码如下：

public class Solution {
    public List<Integer> grayCode(int n) {
        
        List<Integer> list = new ArrayList<Integer>();
        //去除重复
        Set<String> set = new HashSet<String>();

        //表示二进制数的数组
        char[] c = new char[n];
        Arrays.fill(c, '0');//全部为0
        set.add(new String(c));
        list.add(0);
        int i = 1;//从1开始
        //格雷码长度
        int len = (int) Math.pow(2, n);
        while(i++ < len){
        	//逐个尝试
        	for(int j = c.length - 1; j >= 0; j--){
        		c[j] = c[j] == '1' ? '0':'1';//每一位均异或
        		String b = new String(c);
        		//成功则添加结果集，并结束循环
        		if(set.add(b)){
        			//二进制转换为十进制
        			list.add(Integer.valueOf(b, 2));
        			break;
        		}else{
        			//如果不是则数值变换回来
        			c[j] = c[j] == '1' ? '0':'1';
        		}
        	}
        }
        return list;
    }
}

leetCode 89.Gray Code （格雷码） 解题思路和方法

标签：leetcode

原文地址：http://blog.csdn.net/xygy8860/article/details/47053593