89. 格雷编码

原题

https://leetcode.cn/problems/gray-code/description/

思路

位运算

复杂度

时间：O(2ⁿ)
空间：O(2ⁿ)

Python代码

class Solution:
    def grayCode(self, n: int) -> List[int]:
        res, head = [0], 1
        for i in range(n):
            for j in range(len(res) - 1, -1, -1):
                res.append(head + res[j])
            head <<= 1
        return res
       

Go代码

func grayCode(n int) []int {
	res := []int{0}
	head := 1
	for i := 0; i < n; i++ {
		for j := len(res) - 1; j >= 0; j-- {
			res = append(res, head+res[j])
		}
		head <<= 1
	}
	return res
}