89. Gray Code

https://leetcode.com/problems/gray-code/discuss/29893/One-liner-Python-solution-(with-demo-in-comments)

 

 

 

class Solution {
    public List<Integer> grayCode(int n) {
        List<Integer> res = new ArrayList<>();
        res.add(0);
        for(int i = 0; i < n; i++) {
            for(int j = res.size() - 1; j >= 0 ; j--) {
                res.add(res.get(j) + (int)Math.pow(2, i));
            }
        }
        return res;
    }
}