Design HashSet

LeetCode Q 705 - Design HashSet

Design a HashSet without using any built-in hash table libraries.

To be specific, your design should include these functions:

• add(value): Insert a value into the HashSet.
• contains(value) : Return whether the value exists in the HashSet or not.
• remove(value): Remove a value in the HashSet. If the value does not exist in the HashSet, do nothing.

Example:
MyHashSet hashSet = new MyHashSet();
hashSet.add(1);
hashSet.add(2);
hashSet.contains(1); // returns true
hashSet.contains(3); // returns false (not found)
hashSet.add(2);
hashSet.contains(2); // returns true
hashSet.remove(2);
hashSet.contains(2); // returns false (already removed)

Note:

• All values will be in the range of [0, 1000000].
• The number of operations will be in the range of [1, 10000].
• Please do not use the built-in HashSet library.

Solution

Code:

class MyHashSet {

	private boolean[] arr;

	/ * Initialize your data structure here. * /
	public MyHashSet() {
		arr = new boolean[1000001];
	}
	
	public void add(int key) {
		arr[key] = true;
	}
	
	public void remove(int key) {
		arr[key] = false;
	}
	
	/ * Returns true if this set contains the specified element * /
	public boolean contains(int key) {
		return arr[key];
	}
}