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.
根据题目中的意思,我们只要求出一组合适的解即可。正确答案非常精妙(我没有想出来。。。),充分利用位运算。看来对于位运算的知识我还是要再加强。
答案出处:http://www.2cto.com/kf/201305/215316.html
1 class Solution { 2 public: 3 4 vector<int> grayCode(int n) { 5 // Start typing your C/C++ solution below 6 // DO NOT write int main() function 7 vector<int> result; 8 int m=1<<n; 9 for(int i=0;i<m;i++) 10 { 11 result.push_back(i^(i>>1)); 12 } 13 return result; 14 15 } 16 };
思路:首先,1<<n 是用来计算2的n次方。i^(i>>1)是格雷码的计算方法,表示第i个数是几。好久不用都想不起来了。。。