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package g0701_0800.s0705_design_hashset;

// #Easy #Array #Hash_Table #Design #Linked_List #Hash_Function
// #2022_03_23_Time_29_ms_(57.06%)_Space_85_MB_(12.64%)

/**
 * 705 - Design HashSet\.
 *
 * Easy
 *
 * 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`.
**/
public class MyHashSet {

    private final boolean[] arr;

    public MyHashSet() {
        arr = new boolean[1000001];
    }

    public void add(int key) {
        arr[key] = true;
    }

    public void remove(int key) {
        arr[key] = false;
    }

    public boolean contains(int key) {
        return arr[key];
    }
}

/*
 * Your MyHashSet object will be instantiated and called as such:
 * MyHashSet obj = new MyHashSet();
 * obj.add(key);
 * obj.remove(key);
 * boolean param_3 = obj.contains(key);
 */