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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.
n=3时，GrayCode是:
000 001 011 010 110 111 101 100
n位的格雷码可以从n-1位的格雷码得到，
n位的格雷码组成：
1、n-1位的格雷码
2、n-1位的格雷码的逆序+（1<<(n-1)）
如下图：
#include<iostream> #include<vector> using namespace std; // Non_Recursive vector<int> GrayCode_1(int n){ vector<int> result; result.push_back(0); for(int i=0;i<n;i++){ int len=result.size(); int c=1<<i; for(int j=len-1;j>=0;j--) result.push_back(result[j]+c); } return result; } // Recursive void GrayCode_2(vector<int> &result,int n){ if(n==0){ result.push_back(0); return; } GrayCode_2(result,n-1); int len=result.size(); for(int i=len-1;i>=0;i--) result.push_back(result[i]+(1<<(n-1))); } int main(){ int n=4; vector<int> result1; vector<int> result2; result1=GrayCode_1(n); GrayCode_2(result2,n); for(int i=0;i<result1.size();i++) cout<<result1[i]<<" "; cout<<endl; for(int i=0;i<result2.size();i++) cout<<result2[i]<<" "; cout<<endl; return 0; }
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原文地址：http://www.cnblogs.com/AndyJee/p/4789862.html
