Leetcode: Design HashSet

Design HashSet

Similar Problems:

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.


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


  • 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.

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

  • Solution:
// Blog link: https://code.dennyzhang.com/design-hashset
// Basic Ideas:
// Use an array of 1000000 item
// Complexity: Time O(1), Space O(1)
type MyHashSet struct {
    l []bool

/** Initialize your data structure here. */
func Constructor() MyHashSet {
    m := MyHashSet{}
    m.l = make([]bool, 1000001)
    return m

func (this *MyHashSet) Add(key int)  {
    this.l[key] = true

func (this *MyHashSet) Remove(key int)  {
    this.l[key] = false

/** Returns true if this set contains the specified element */
func (this *MyHashSet) Contains(key int) bool {
    return this.l[key]

 * Your MyHashSet object will be instantiated and called as such:
 * obj := Constructor();
 * obj.Add(key);
 * obj.Remove(key);
 * param_3 := obj.Contains(key);

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