首页 > 代码库 > LeetCode Gray Code

LeetCode Gray Code

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 - 001 - 111 - 310 - 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.

 

解法:使用递归或者迭代的思想。每次增加一位,最高位就增加了0,后者1.最高位是0的情况就是n-1的解,最高位是1的情况就是n-1的解的倒序加上一个2的指数。

 1 public class Solution { 2     List<Integer> before=new ArrayList<>(Arrays.asList(0,1)); 3     int pluss=1; 4     public List<Integer> grayCode(int n) { 5             List<Integer> list=new ArrayList<>(); 6             list.add(0); 7             if (n==0) { 8                 return list; 9             }10             if (n==1) {11                 list.add(1);12                 return list;13             }14             list.add(1);15             for (int i = 1; i < n; i++) {16                 pluss=pluss*2;17                 for (int j = before.size()-1; j >=0 ; j--) {18                     list.add(before.get(j)+pluss);19                 }20                 before=list;21             }22             return list;23     }24 }

 

LeetCode Gray Code