题解 | #生成格雷码#

import java.util.*;

public class GrayCode {
    public String[] getGray(int n) {
        // write code here
        String[] ans = new String[(int) Math.pow(2, n)];
        ans[0] = "0";
        ans[1] = "1";
        int len = 2, len2 = len << 1;
        for(int i = 1; i < n; i++) {
            for(int j = len; j < len2; j++) {
                ans[j] = "1" + ans[len - 1 - j + len];
            }
            for(int j = 0; j < len; j++) {
                ans[j] = "0" + ans[j];
            }
            len = len2;
            len2 = len << 1;
        }
        return ans;
    }
}