题目:
https://leetcode.com/problems/counting-bits/
难度: Medium
O(n*sizeof(integer)) 算法，其实就是把count of 1 bit拿来用：
class Solution(object):
def countBits(self, num):
"""
:type num: int
:rtype: List[int]
"""
def hammingWeight(n):
cnt = 0
while n != 0:
n &= n -1
cnt += 1
return cnt
res = []
for i in range(num+1):
res.append(hammingWeight(i))
return res
DP算法 - to be done