[LeetCode] 033: Gray Code

[Problem]
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.

[Solution]

class Solution {
public:
// get the nthBit, index starts from 0
int nthBit(int num, int n){
return num & (1 << n);
}
// convert integer to gray
int int2gray(int num, int n){
for(int i = 0; i < n-1; ++i){
int XOR = nthBit(num, i) ^ (nthBit(num, i+1)>>1);
num = num & (~nthBit(num, i)) | XOR;
}
return num;
}
// get gray codes with n bits
vector<int> grayCode(int n) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
vector<int> res;
if(n < 0){
return res;
}
if(n == 0){
res.push_back(0);
return res;
}

// generate
int m = pow(2, n);
for(int i = 0; i < m; ++i){
res.push_back(int2gray(i, n));
}
return res;
}
};

说明：版权所有，转载请注明出处。Coder007的博客