89. 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.

Example 1:

Input:  2
Output:  [0,1,3,2]
Explanation:
00 - 0
01 - 1
11 - 3
10 - 2

For a given  _n_ , a gray code sequence may not be uniquely defined.
For example, [0,2,3,1] is also a valid gray code sequence.

00 - 0
10 - 2
11 - 3
01 - 1

Example 2:

Input:  0
Output:  [0]
Explanation: We define the gray code sequence to begin with 0.
             A gray code sequence of _n_ has size = 2n, which for _n_ = 0 the size is 20 = 1.
             Therefore, for _n_ = 0 the gray code sequence is [0].

# @lc code=start
using LeetCode

function gray_code(N::Int)
    powN = 1 << N
    res = Array{Int}(undef, powN)
    for i in 0:powN-1
        res[i + 1] = i ⊻ (i >> 1);
    end
    res
end
# @lc code=end

gray_code (generic function with 1 method)

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