数据结构源码

实现类

import java.util.TreeMap;

public class HashTable<K, V> {

    private static final int upperTol = 10;

    private static final int lowerTol = 2;

    private static final int initCapacity = 7;

    private TreeMap<K, V>[] hashtable;

    private int M;

    private int size;

    public HashTable(int M) {
        this.M = M;
        size = 0;
        hashtable = new TreeMap[M];
        for (int i = 0; i < M; i++) {
            hashtable[i] = new TreeMap<>();
        }
    }

    public HashTable() {
        this(initCapacity);
    }

    private int hash(K key) {
        return (key.hashCode() & 0x7fffffff) % M;
    }

    public int getSize() {
        return size;
    }

    public void add(K key, V value) {
        TreeMap<K, V> map = hashtable[hash(key)];

        if (!map.containsKey(key)){
            map.put(key, value);
            size ++;

            if(size >= upperTol * M)
                resize(2 * M);
        }
    }

    public V remove(K key) {
        TreeMap<K, V> map = hashtable[hash(key)];
        V ret = null;
        if (map.containsKey(key)) {
            ret = map.remove(key);
            size--;

            if (size < lowerTol * M && M / 2 > 0)
                resize(M / 2);
        }
        return ret;
    }

    public void set(K key, V value) {
        TreeMap<K, V> map = hashtable[hash(key)];
        if (!map.containsKey(key)) {
            throw new IllegalArgumentException(key + " doesn't exist!");
        }
        map.put(key, value);
    }

    public boolean contains(K key) {
        return hashtable[hash(key)].containsKey(key);
    }

    public V get(K key) {
        return hashtable[hash(key)].get(key);
    }

    private void resize(int newM){
        TreeMap<K, V>[] newHashTable = new TreeMap[newM];
        for(int i = 0 ; i < newM ; i ++)
            newHashTable[i] = new TreeMap<>();

        for(int i = 0 ; i < M ; i ++)
            for(K key: hashtable[i].keySet())
                newHashTable[hash(key)].put(key, hashtable[i].get(key));

        this.M = newM;
        this.hashtable = newHashTable;
    }
}

数据结构拆解

维护字段和内部类

private static final int upperTol = 10;

private static final int lowerTol = 2;

private static final int initCapacity = 7;

private TreeMap<K, V>[] hashtable;

private int M;

private int size;

构造函数

public HashTable(int M) {
    this.M = M;
    size = 0;
    hashtable = new TreeMap[M];
    for (int i = 0; i < M; i++) {
        hashtable[i] = new TreeMap<>();
    }
}

public HashTable() {
    this(initCapacity);
}

增

public void add(K key, V value) {
    TreeMap<K, V> map = hashtable[hash(key)];

    if (!map.containsKey(key)){
        map.put(key, value);
        size ++;

        if(size >= upperTol * M)
            resize(2 * M);
    }
}

删

public V remove(K key) {
    TreeMap<K, V> map = hashtable[hash(key)];
    V ret = null;
    if (map.containsKey(key)) {
        ret = map.remove(key);
        size--;

        if (size < lowerTol * M && M / 2 > 0)
            resize(M / 2);
    }
    return ret;
}

改

public void set(K key, V value) {
    TreeMap<K, V> map = hashtable[hash(key)];
    if (!map.containsKey(key)) {
        throw new IllegalArgumentException(key + " doesn't exist!");
    }
    map.put(key, value);
}

private void resize(int newM){
    TreeMap<K, V>[] newHashTable = new TreeMap[newM];
    for(int i = 0 ; i < newM ; i ++)
        newHashTable[i] = new TreeMap<>();

    for(int i = 0 ; i < M ; i ++)
        for(K key: hashtable[i].keySet())
            newHashTable[hash(key)].put(key, hashtable[i].get(key));

    this.M = newM;
    this.hashtable = newHashTable;
}

查

private int hash(K key) {
    return (key.hashCode() & 0x7fffffff) % M;
}

public int getSize() {
    return size;
}

public boolean contains(K key) {
    return hashtable[hash(key)].containsKey(key);
}

public V get(K key) {
    return hashtable[hash(key)].get(key);
}