leecode_338 Counting Bits

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:

Fornum = 5 you should return [0,1,1,2,1,2].

i如果是偶数，则1的位数和i/2相等，如果是奇数，醉靠近他的一个偶数末尾为0，所以+1就行

c++实现：

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