solve.cpp

#include <vector>
#include <string>
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <unordered_set>
using namespace std;
class Solution {
	public:
		vector<int> grayCode(int n) {
			return grayCode2(n);
		}
	private:
		vector<int> grayCode1(int n) {
			vector<int> result;
			for (int i = 0; i < (1 << n); ++i) {
				result.push_back(i ^ (i >> 1));
			}
			return result;
		}
		vector<int> grayCode2(int n) {
			vector<int> result;
			result.push_back(0);
			for (int i = 0; i < n; ++i) {
				int high = 1 << i;
				for (int j = result.size() - 1; j >= 0; --j)
					result.push_back(result[j] + high);
			}
			return result;
		}
};
void print(vector<int> v)
{
	cout << "[";
	for_each(begin(v), end(v), [](int i){cout << i << ' ';});
	cout << "]";
	cout << endl;
}
int main(int argc, char **argv)
{
	Solution solution;
	int n;
	while (cin >> n) {
		print(solution.grayCode(n));
	}
	return 0;
}