Counting Bits（Difficulty: Medium）

题目：

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].

实现：

 1 class Solution {
 2 public:
 3     vector<int> countBits(int num) {
 4    vector<int> result;
 5     for (int i = 0; i <= num; i++)
 6     {
 7         int count = 0;
 8         int j = i;
 9         while (j)
10         {
11             ++count;
12             j = (j-1) & j;
13         }
14         result.push_back(count);
15     }
16     return result;
17     }
18 };