Gray Code

Desicription

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:

1
2
3
4
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.

Solution

1
2
3
4
5
6
7
8
9
10
11
12
13
14
class Solution {
public:
vector<int> grayCode(int n) {
vector<int> res(1, 0);
for(int i = 0; i < n; i++) {
int cur_size = res.size();
while(cur_size) {
cur_size--;
res.push_back(res[cur_size] + (1<<i));
}
}
return res;
}
};