求0~n里面每个数二进制1的个数，用o(n)算法

338. Counting Bits

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Question Editorial Solution

Total Accepted: 20178  Total Submissions: 36151  Difficulty: Medium

Given a non negative integer number num. For every numbers i in the range 0 ≤ i ≤ num calculate the number of 1's in their binary representation and return them as an array.

Example:
For num = 5 you should return [0,1,1,2,1,2].

clclass Solution {
public:
vector<int> countBits(int num) {
       vector<int>ans;
       ans.push_back(0);
       int res=0;
       for(int i=1;i<=num;i++)
       {
           if((i&(i-1))==0) 
               {
                   res=i;
                   ans.push_back(1);
               }
           else 
           {
               ans.push_back(ans[i-res]+1);
           }
       }
       return ans;
   }
};