705. Design HashSet (Easy)

https://leetcode.com/problems/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.

Hints

Solutions

http://copyfuture.com/blogs-details/2047a90be3e3713072a453aaa1d12100

class MyHashSet {
    private List<Integer> list = null;
    public MyHashSet() {
        list=new ArrayList<>();
    }

    public void add(int key) {
        list.add(key);
    }
    public void remove(int key) {
        for (int i = list.size() - 1; i >= 0; i--) {
            if (list.get(i) == key) {
                list.remove(i);
            }
        }
    }
    public boolean contains(int key) {
        return list.contains(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);
 */
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