338. 比特位计数

class Solution 
{
public:
    vector<int> countBits(int num) 
    {
        vector<int> res;
        for(int i = 0;i <= num;i ++)
        {
            int count = 0;
            for(int k = 0;k < 32;k ++) count += ((i >> k) & 1);
            res.push_back(count);
        }
        return res;
    }
};