[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 - 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.

参照格雷码

public class Solution {
    public List
  
    grayCode(int n) {
    	List
   
     list = new ArrayList<>(); List
    
      str = help(n); for(int i=0;i
     
       help(int n){ List
      
        list = new ArrayList<>(); if(n==0) { list.add("0"); return list; } if(n==1){ list.add("0"); list.add("1"); return list; } List
       
         lin = help(n-1); List
        
          res = new ArrayList<>(); for(int i=0;i
         
          =0;i--){ String str = "1"+lin.get(i); res.add(str); } return res; } }