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].
Follow up:
- It is very easy to come up with a solution with run time O(n*sizeof(integer)). But can you do it in linear time O(n) /possibly in a single pass?
- Space complexity should be O(n).
- Can you do it like a boss? Do it without using any builtin function like __builtin_popcount in c++ or in any other language.
1 class Solution { 2 public: 3 vector<int> countBits(int num) { 4 vector<int> ret(num+1, 0); 5 for (int i = 1; i <= num; ++i) 6 ret[i] = ret[i&(i-1)] + 1; 7 return ret; 8 } 9 };