# Set

Implement a set data structure with the following methods:

`CustomSet()`

constructs a new instance of a set`add(int val)`

adds`val`

to the set`exists(int val)`

returns whether`val`

exists in the set`remove(int val)`

removes the`val`

in the set

This should be implemented without using built-in set.

**Constraints**

`n ≤ 100,000`

where`n`

is the number of calls to`add`

,`exists`

and`remove`

https://binarysearch.com/problems/Set

## Examples

### Example 1

**Input**

- methods =
`['constructor', 'add', 'exists', 'remove', 'exists']`

- arguments =
`[[], [1], [1], [1], [1]]`

**Output**

- answer =
`[None, None, True, None, False]`

**Explanation**

```
c = CustomSet()
c.add(1)
c.exists(1) == True
c.remove(1)
c.exists(1) == False
```

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