Gray-Code

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题目地址

LeetCode#89 Gray Code

题目描述

  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.

解题思路

  思路比较简单，直接遍历就可以了，看代码。

解题代码

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class Solution {
public:
    vector<int> grayCode(int n) {
        vector<int> ret(0);
        ret.push_back(0);
        if (n == 0) return ret;
        ret.push_back(1);
        for (int i = 1; i < n; ++i) {
            int size = ret.size();
            for (int j = size - 1; j >= 0; --j) {
                ret.push_back(static_cast<int &&>(ret[j] + pow(2 , i)));
            }
        }
        return ret;
    }
};
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