Gray Code

• leetcode

Description

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.

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Formula

g0 = b0, gi= b(i - 1) XO b(i)

(i ^(i>>1))

Java Solution

public class Solution {
    public List<Integer> grayCode(int n) {
        List<Integer> res = new LinkedList<>();
        int size = 1 << n;
        for(int i = 0; i < size; ++i){
            res.add(i ^ (i >> 1));
        }
        return res;
    }
}

C++ Solution

class Solution {
public:
    vector<int> grayCode(int n) {
        vector<int> result;
        size_t size=1<<n;
        result.reserve(size);

        for(size_t i=0;i<size;++i){
            result.push_back(i^(i>>1));
        }

        return result;
    }
};

Comment

Very Boring, just remember the formula.