705-design-hashset

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Description

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.

Solution(Python)

class MyHashSet:
    def eval_hash(self, key):
        return key % (1 << 15)

    def __init__(self):
        self.arr = [[] for _ in range(1 << 15)]

    def add(self, key: int) -> None:
        t = self.eval_hash(key)
        if key not in self.arr[t]:
            self.arr[t].append(key)

    def remove(self, key: int) -> None:
        t = self.eval_hash(key)
        if key in self.arr[t]:
            self.arr[t].remove(key)

    def contains(self, key: int) -> bool:
        t = self.eval_hash(key)
        return key in self.arr[t]