89. 格雷编码

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Java代码：2DFS

class Solution {List<Integer> res = new ArrayList<>();public List<Integer> grayCode(int n) {dfs(n, new StringBuffer(), new int[]{0, 1});return res;}public void dfs(int n, StringBuffer sb, int[] nums){if(sb.length() == n){res.add(Integer.valueOf(sb.toString(), 2));return;}sb.append(nums[0]);dfs(n, sb, new int[]{0,1});sb.deleteCharAt(sb.length() - 1);sb.append(nums[1]);dfs(n, sb, new int[]{1, 0});sb.deleteCharAt(sb.length() - 1);}
}