## 705. Design HashSet

Design a HashSet without using any built-in hash table libraries.

Implement `MyHashSet` class:

• `void add(key)` Inserts the value `key` into the HashSet.
• `bool contains(key)` Returns whether the value `key` exists in the HashSet or not.
• `void remove(key)` Removes the value `key` in the HashSet. If `key` does not exist in the HashSet, do nothing.

Example 1:

```Input
[[], [1], [2], [1], [3], [2], [2], [2], [2]]
Output
[null, null, null, true, false, null, true, null, false]

Explanation
MyHashSet myHashSet = new MyHashSet();
myHashSet.add(2);      // set = [1, 2]
myHashSet.contains(1); // return True
myHashSet.add(2);      // set = [1, 2]
myHashSet.contains(2); // return True
myHashSet.remove(2);   // set = [1]
myHashSet.contains(2); // return False, (already removed)```

Constraints:

• `0 <= key <= 106`
• At most `104` calls will be made to `add`, `remove`, and `contains`.

Follow up: Could you solve the problem without using the built-in HashSet library?

## Rust Solution

``````#[derive(Default)]
struct MyHashSet {
table: Vec<bool>,
}

impl MyHashSet {
fn new() -> Self {
MyHashSet {
table: vec![false; 1_000_000],
}
}
fn add(&mut self, key: i32) {
self.table[key as usize] = true;
}
fn remove(&mut self, key: i32) {
self.table[key as usize] = false;
}
fn contains(&self, key: i32) -> bool {
self.table[key as usize]
}
}

#[test]
fn test() {
let mut hs = MyHashSet::new();