使用dp思想，dp[n] = dp[n /2] （最后一位是0）或者 dp[n /2] + 1（最后一位是1）

class Solution {
public:
    vector<int> countBits(int num) {
        vector<int> result;
        if(num >= 0)
            result.push_back(0);
        if(num >= 1)
            result.push_back(1);
        if(num >= 2) {
            for(int i = 2; i <= num; i++) {
                int onetimes = i % 2 == 0 ? result[i / 2] : result[i / 2] + 1;
                result.push_back(onetimes);
            }
        }
        
        return result;
    }
};