【Leetcode】Gray Code

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.

class Solution {
public:
vector<int> grayCode(int n) {
int size = 1 << n;
vector<int> ret;
ret.resize(size);
for (int i = 0; i < size; i++){
ret[i] = i ^ i>>1;
}
return ret;
}
};

View Code
用公式吧，多快好省啊...

gray(i) = i ^ (i >> 1)