705.design-hashset.java

/*
 * @lc app=leetcode id=705 lang=java
 *
 * [705] Design HashSet
 *
 * https://leetcode.com/problems/design-hashset/description/
 *
 * algorithms
 * Easy (54.98%)
 * Total Accepted:    40.3K
 * Total Submissions: 68.8K
 * Testcase Example:  '["MyHashSet","add","add","contains","contains","add","contains","remove","contains"]\n[[],[1],[2],[1],[3],[2],[2],[2],[2]]'
 *
 * 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.
 *
 *
 */
 class MyHashSet {

     List<Integer> values;

     /** Initialize your data structure here. */
     public MyHashSet() {
         values = new ArrayList<>();
     }

     public void add(int key) {
         for (int num : values) {
             if (num == key) {
                 return;
             }
         }

         values.add(key);
     }

     public void remove(int key) {
         values.remove(new Integer(key));
     }

     /** Returns true if this set contains the specified element */
     public boolean contains(int key) {
         return values.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);
 */