题目

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:

  1. MyHashSet hashSet = new MyHashSet();
  2. hashSet.add(1);         
  3. hashSet.add(2);         
  4. hashSet.contains(1);    // returns true
  5. hashSet.contains(3);    // returns false (not found)
  6. hashSet.add(2);          
  7. hashSet.contains(2);    // returns true
  8. hashSet.remove(2);          
  9. 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.

题意

实现一个只有add、contains、remove三个方法的HashSet。

思路

直接开一个boolean数组进行hash。

代码实现

Java

  1. class MyHashSet {
  2.     private boolean[] hash;
  4.     /** Initialize your data structure here. */
  5.     public MyHashSet() {
  6.         hash = new boolean[1000001];
  7.     }
  9.     public void add(int key) {
  10.         hash[key] = true;
  11.     }
  13.     public void remove(int key) {
  14.         hash[key] = false;
  15.     }
  17.     /** Returns true if this set contains the specified element */
  18.     public boolean contains(int key) {
  19.         return hash[key];
  20.     }
  21. }
  23. /**
  24.  * Your MyHashSet object will be instantiated and called as such:
  25.  * MyHashSet obj = new MyHashSet();
  26.  * obj.add(key);
  27.  * obj.remove(key);
  28.  * boolean param_3 = obj.contains(key);
  29.  */