Java 資料結構雜湊演演算法之雜湊桶方式解決雜湊衝突

public class HashBucket {

    static class Node {//使用內部類方式定義節點
        public int key;
        public int val;
        public Node next;

        public Node(int key, int val) {
            this.key = key;
            this.val = val;
        }
    }

    private Node[] array;
    public int usedSize;

    public HashBucket() {
        this.array = new Node[10];
        this.usedSize = 0;
    }


    public void put(int key,int val) {//存放資料
        //1、確定下標
        int index = key % this.array.length;
        //2、遍歷這個下標的連結串列
        Node cur = array[index];
        while (cur != null) {
            //更新val
            if(cur.key == key) {
                cur.val = val;
                return;
            }
            cur = cur.next;
        }
        //3、cur == null   當前陣列下標的連結串列中沒有key
        Node node = new Node(key,val);
        node.next = array[index];
        array[index] = node;
        this.usedSize++;
        //4、判斷當前有沒有超過負載因子
        if(loadFactor() >= 0.75) {//負載因子我們認為0.75
            //擴容
            resize();
        }
    }

    public int get(int key) {//取出資料
        //以什麼方式儲存的  那就以什麼方式取
        int index = key % this.array.length;

        Node cur = array[index];

        while (cur != null) {
            if(cur.key == key) {
                return cur.val;
            }
            cur = cur.next;
        }

        return -1;
    }


    public double loadFactor() {//計算負載因子
        return this.usedSize*1.0 / this.array.length;
    }

    public void resize() {//擴容函數
        //自己建立新的2倍陣列
        Node[] newArray = new Node[2*this.array.length];
        //遍歷原來的雜湊桶
        //最外層迴圈 控制陣列下標
        for (int i = 0; i < this.array.length; i++) {
            Node cur = array[i];
            Node curNext = null;
            while (cur != null) {
                //記錄cur.next
                curNext = cur.next;
                //在新的陣列裡面的下標
                int index = cur.key % newArray.length;
                //進行頭插法
                cur.next = newArray[index];
                newArray[index] = cur;
                cur = curNext;
            }
        }
        this.array = newArray;
    }

class Person {
    public String id;

    public Person(String id) {
        this.id = id;
    }

    @Override
    public String toString() {
        return "Person{" +
                "id='" + id + ''' +
                '}';
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Person person = (Person) o;
        return Objects.equals(id, person.id);
    }

    @Override
    public int hashCode() {
        return Objects.hash(id);
    }
}
public class HashBuck2<K,V> {
    static class Node<K,V> {
        public K key;
        public V val;
        public Node<K,V> next;

        public Node(K key,V val) {
            this.key = key;
            this.val = val;
        }
    }


    public Node<K,V>[] array = (Node<K, V>[]) new Node[10];
    public int usedSize;

    public void put(K key,V val) {
        //通過hashcode方法定位陣列的下標
        int hash = key.hashCode();
        int index = hash % this.array.length;
        Node<K,V> cur = array[index];
        while (cur != null) {
            //equals 起的作用是遍歷當前陣列下標的key是否相同
            if(cur.key.equals(key)) {
                cur.val = val;
            }
            cur = cur.next;
        }

        Node<K,V> node = new Node<>(key,val);
        node.next = array[index];
        array[index] = node;
        this.usedSize++;
    }

    public V get(K key) {
        int hash = key.hashCode();
        int index = hash % this.array.length;
        Node<K,V> cur= array[index];
        while (cur != null) {
            if(cur.key.equals(key)) {
                return cur.val;
            }
            cur = cur.next;
        }
        return null;
    }