RUST GYM Leetcode 705 Design HashSet Rust Solution

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
["MyHashSet", "add", "add", "contains", "contains", "add", "contains", "remove", "contains"]
[[], [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(1);      // set = [1]
myHashSet.add(2);      // set = [1, 2]
myHashSet.contains(1); // return True
myHashSet.contains(3); // return False, (not found)
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();
    hs.add(1);
    hs.add(2);
    assert_eq!(hs.contains(1), true);
    assert_eq!(hs.contains(3), false);
    hs.add(2);
    assert_eq!(hs.contains(2), true);
    hs.remove(2);
    assert_eq!(hs.contains(2), false);
}

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