# Day 28 of 31-Day May LeetCode Challenge

1 min readMay 28, 2020

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

**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.