首页 > itarticle > [leetcode] problem 705 – design hashset

[leetcode] problem 705 – design hashset

admin 11月 13, 2020 0

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);    
hashSet.contains(3);    // returns false (not found)
hashSet.add(2);          
hashSet.contains(2);    
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.

Code

private int size = 1000;
private LinkedList[] map;

public () {
    map = new LinkedList[size];

    for (int i = 0; i < size; i++)
        map[i] = new LinkedList<Integer>();
}

public void add(int key) {
    if (!contains(key)) {
        int hash = hash(key);
        map[hash].add(key);
    }
}

public void remove(int key) {
    if (contains(key)) {
        int hash = hash(key);
        int idx = map[hash].indexOf(key);
        map[hash].remove(idx);
    }
}

public boolean contains(int key) {
    int hash = hash(key);
    return map[hash].contains(key);
}

private int hash(Integer x){
    return x.hashCode() % size;
}