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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