# Problem Definition

## Description

Design and implement a TwoSum class. It should support the following operations: `add` and `find`.

`add` - Add the number to an internal data structure.
`find` - Find if there exists any pair of numbers which sum is equal to the value.

**Example 1:**

```plaintext
add(1); add(3); add(5);
find(4) -> true
find(7) -> false
```

**Example 2:**

```plaintext
add(3); add(1); add(2);
find(3) -> true
find(6) -> false
```

## Notes

1. [LeetCode discussion - Trade off in this problem should be considered](https://leetcode.com/problems/two-sum-iii-data-structure-design/discuss/52005/Trade-off-in-this-problem-should-be-considered)