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.
这道题可以用迭代的方法在数字之前加1,每次从list的最后一位向前迭代。代码如下:public class Solution {
public List<Integer> grayCode(int n) {
List<Integer> list = new ArrayList<Integer>();
list.add(0);
for (int i = 0; i < n; i ++) {
int size = list.size();
int add = 1 << i;
for (int j = size - 1; j >= 0; j --) {
list.add(list.get(j) + add);
}
}
return list;
}
}