## 1. Problem

Given an integer n, return an array ans of length n + 1 such that for each i (0 <= i <= n), ans[i] is the number of 1’s in the binary representation of i.

Example 1:

```
Input: n = 2
Output: [0,1,1]
Explanation:
0 --> 0
1 --> 1
2 --> 10
```

Example 2:

```
Input: n = 5
Output: [0,1,1,2,1,2]
Explanation:
0 --> 0
1 --> 1
2 --> 10
3 --> 11
4 --> 100
5 --> 101
```

Constraints:

- 1 <= s.length <= 10^5

## 2. Solution

I solved this problem like this.

```
class Solution:
def countBits(self, n: int) -> List[int]:
return [bin(x)[2:].count('1') for x in range(n+1)]
```