[LeetCode] Gray Code

標籤：c++   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 - 001 - 111 - 310 - 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.

解題思路：

格雷碼，相鄰兩個二進位之間只有一位不同。n位二進位的格雷碼的數目是2^n個，且第i個格雷碼為(i>>1)^i。估計題目有點問題，當n為0時，應該返回{}，但是這裡要求返回{0}

class Solution {public:    vector<int> grayCode(int n) {        vector<int> result;        if(n<0){            return result;        }        int num = 1<<n;        for(int i=0; i<num; i++){            result.push_back((i>>1)^i);        }        return result;    }};

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[LeetCode] Gray Code