LeetCode 705. Design HashSet

Design a HashSet without using any built-in hash table libraries. You may not use set() or dict().

Implement the MyHashSet class:

• MyHashSet() initializes the object with an empty set.
• add(key) Inserts the value key into the HashSet.
• contains(key) Returns whether the value key exists in the HashSet or not.
• remove(key) Removes the value key in the HashSet. If key does not exist in the HashSet, do nothing.

Examples

Example 1

Input:  ["MyHashSet()", "add(1)", "add(2)", "contains(1)", "contains(3)", "add(2)", "contains(2)", "remove(2)", "contains(2)"]
Output: [null, null, null, true, false, null, true, null, false]

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 <= 1,000,000
• At most 10,000 calls will be made to add, remove, and contains.

How the tests work: each test is a sequence of calls. operations[i] is the method called with arguments[i]; the first entry constructs the class. The expected output lists what every call returns — null for the constructor and for methods that return nothing.