Gray Code

leetcode 里面Gray code题的多种解法

#include<iostream>
#include<vector>
#include<stack>
using namespace std;

class Solution1
{
public:
    vector<int>grayCode(int n)
    {
        vector<int>result;
        vector<int>temp;
        if(n==0)
        {
            result.push_back(0);
            return result;
        }
        if(n==1)
        {
            result.push_back(0);
            result.push_back(1);
            return result;
        }
        else
        {
            result=grayCode(n-1);

        }
        temp=result;

        for(vector<int>::reverse_iterator iter=temp.rbegin();iter!=temp.rend();iter++)
            result.push_back(*iter+pow(2,n-1));
        /*reverse(temp.begin(),temp.end());
        for(vector<int>::iterator iter=temp.begin();iter<temp.end();iter++)
            result.push_back(*iter+pow(2,n-1));*/
        //temp.erase(temp.begin(),temp.end());
        return result;
    }

};

class Solution2
{
public:
    vector<int> grayCode(int n) {
    vector<int> result;
    const size_t size = 1 << n; 
    result.reserve(size);
    for (size_t i = 0; i < size; ++i)
        result.push_back(binary_to_gray(i));
    return result;
    }
        private:
        static unsigned int binary_to_gray(unsigned int n) {
        return n ^ (n >> 1);
    }
};

class Solution3 
{
public:
    vector<int> grayCode(int n) {
    vector<int> result;
    result.reserve(1<<n);
    result.push_back(0);
    for (int i = 0; i < n; i++) {
    const int highest_bit = 1 << i;
    for (int j = result.size() - 1; j >= 0; j--)
    result.push_back(highest_bit | result[j]);
    }
    return result;
    }
};

class Solution4
{
public:
    vector<int>grayCode(int n)
    {
        vector<int>result;
        int num;
        result.push_back(0);
        for(int i=0;i<n;i++)
        {
            num=1<<i;
            for(int j=result.size()-1;j>=0;j--)
                result.push_back(result[j]+num);
        }

    return result;
    }
};
void main()
{
    Solution1 solution;
    vector<int>array;
    array=solution.grayCode(5);
    for(vector<int>::iterator iter=array.begin();iter!=array.end();iter++)
        cout<<*iter<<' ';
    cout<<endl;
    Solution2 solution2;
    vector<int>result;
    result=solution2.grayCode(5);
    for(vector<int>::iterator iter=result.begin();iter!=result.end();iter++)
        cout<<*iter<<' ';
    cout<<endl;

}