0705. Design HashSet (E)

Design HashSet (E)

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:

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.

---

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

class MyHashSet {
    private boolean[] hash;

    /** Initialize your data structure here. */
    public MyHashSet() {
        hash = new boolean[1000001];
    }

    public void add(int key) {
        hash[key] = true;
    }

    public void remove(int key) {
        hash[key] = false;
    }

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