Solution (leetcode-in-java 1.21 API)

java.lang.Object
- g0301_0400.s0338_counting_bits.Solution

```
public class Solution
extends Object
```
338 - Counting Bits.
Easy

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:
- 0 <= n <= 10⁵
Follow up:
- It is very easy to come up with a solution with a runtime of O(n log n). Can you do it in linear time O(n) and possibly in a single pass?
- Can you do it without using any built-in function (i.e., like __builtin_popcount in C++)?

- Constructor Summary
  
  Constructors
  Constructor Description
  
  Solution()
- Method Summary
  
  All Methods Instance Methods Concrete Methods
  Modifier and Type Method Description
  
  int[] countBits(int num)
  - Methods inherited from class java.lang.Object
    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail
- Solution
```
public Solution()
```

Method Detail
- countBits
```
public int[] countBits(int num)
```