Enstringmiento de tablas hash con listas doblemente enlazadas

Requisito previo: Introducción al hash , Hashtable usando una lista enlazada individualmente e implementando nuestra propia tabla hash con enstringmiento separado en Java Implementar una tabla hash usando enstringmiento a través de una lista doblemente enlazada es similar a implementar Hashtable usando una lista enlazada individualmente . La única diferencia es que cada Node de la lista enlazada tiene la dirección tanto del Node siguiente como del anterior. Esto acelerará el proceso de agregar y eliminar elementos de la lista, por lo que la complejidad del tiempo se reducirá drásticamente. Ejemplo:

Si tenemos una lista enlazada individualmente:

1->2->3->4

Si estamos en 3 y es necesario eliminarlo, entonces 2 debe vincularse con 4 y, a partir de 3, no se puede acceder a 2 ya que es una lista vinculada individualmente. Por lo tanto, la lista debe recorrerse nuevamente, es decir, O (n), pero si tenemos una lista doblemente enlazada, es decir,

1<->2<->3<->4

Se puede acceder a 2 y 4 desde 3, por lo tanto, en O(1), 3 se puede eliminar.

A continuación se muestra la implementación del enfoque anterior: 

// C++ implementation of Hashtable
// using doubly linked list
#include <bits/stdc++.h>
using namespace std;
 
const int tablesize = 25;
 
// declaration of node
struct hash_node {
    int val, key;
    hash_node* next;
    hash_node* prev;
};
 
// hashmap's declaration
class HashMap {
public:
    hash_node **hashtable, **top;
 
    // constructor
    HashMap()
    {
        // create a empty hashtable
        hashtable = new hash_node*[tablesize];
        top = new hash_node*[tablesize];
        for (int i = 0; i < tablesize; i++) {
            hashtable[i] = NULL;
            top[i] = NULL;
        }
    }
 
    // destructor
    ~HashMap()
    {
        delete[] hashtable;
    }
 
    // hash function definition
    int HashFunc(int key)
    {
        return key % tablesize;
    }
 
    // searching method
    void find(int key)
    {
        // Applying hashFunc to find
        // index for given key
        int hash_val = HashFunc(key);
        bool flag = false;
        hash_node* entry = hashtable[hash_val];
 
        // if hashtable at that index has some
        // values stored
        if (entry != NULL) {
            while (entry != NULL) {
                if (entry->key == key) {
                    flag = true;
                }
                if (flag) {
                    cout << "Element found at key "
                         << key << ": ";
                    cout << entry->val << endl;
                }
                entry = entry->next;
            }
        }
        if (!flag)
            cout << "No Element found at key "
                 << key << endl;
    }
 
    // removing an element
    void remove(int key)
    {
        // Applying hashFunc to find
        // index for given key
        int hash_val = HashFunc(key);
        hash_node* entry = hashtable[hash_val];
        if (entry->key != key || entry == NULL) {
            cout << "Couldn't find any element at this key "
                 << key << endl;
            return;
        }
 
        // if some values are present at that key &
        // traversing the list and removing all values
        while (entry != NULL) {
            if (entry->next == NULL) {
                if (entry->prev == NULL) {
                    hashtable[hash_val] = NULL;
                    top[hash_val] = NULL;
                    delete entry;
                    break;
                }
                else {
                    top[hash_val] = entry->prev;
                    top[hash_val]->next = NULL;
                    delete entry;
                    entry = top[hash_val];
                }
            }
            entry = entry->next;
        }
        cout << "Element was successfully removed at the key "
             << key << endl;
    }
 
    // inserting method
    void add(int key, int value)
    {
        // Applying hashFunc to find
        // index for given key
        int hash_val = HashFunc(key);
        hash_node* entry = hashtable[hash_val];
 
        // if key has no value stored
        if (entry == NULL) {
            // creating new node
            entry = new hash_node;
            entry->val = value;
            entry->key = key;
            entry->next = NULL;
            entry->prev = NULL;
            hashtable[hash_val] = entry;
            top[hash_val] = entry;
        }
 
        // if some values are present
        else {
            // traversing till the end of
            // the list
            while (entry != NULL)
                entry = entry->next;
 
            // creating the new node
            entry = new hash_node;
            entry->val = value;
            entry->key = key;
            entry->next = NULL;
            entry->prev = top[hash_val];
            top[hash_val]->next = entry;
            top[hash_val] = entry;
        }
        cout << "Value " << value << " was successfully"
                " added at key " << key << endl;
    }
};
 
// Driver Code
int main()
{
    HashMap hash;
    hash.add(4, 5);
    hash.find(4);
    hash.remove(4);
    return 0;
}

// Java implementation of Hashtable
// using doubly linked list
 
class GFG {
 
    static final int tablesize = 25;
 
    // declaration of node
    static class hash_node {
        int val, key;
        hash_node next;
        hash_node prev;
    }
 
    // hashmap's declaration
    static class HashMap {
        hash_node hashtable[], top[];
 
        // constructor
        HashMap()
        {
            // create a empty hashtable
            hashtable = new hash_node[tablesize];
            top = new hash_node[tablesize];
            for (int i = 0; i < tablesize; i++) {
                hashtable[i] = null;
                top[i] = null;
            }
        }
 
        // hash function definition
        int HashFunc(int key) { return key % tablesize; }
 
        // searching method
        void find(int key)
        {
            // Applying hashFunc to find
            // index for given key
            int hash_val = HashFunc(key);
            boolean flag = false;
            hash_node entry = hashtable[hash_val];
 
            // if hashtable at that index has some
            // values stored
            if (entry != null) {
                while (entry != null) {
                    if (entry.key == key) {
                        flag = true;
                    }
                    if (flag) {
                        System.out.println(
                            "Element found at key " + key
                            + ": " + entry.val);
                    }
                    entry = entry.next;
                }
            }
            if (!flag)
                System.out.println(
                    "No Element found at key " + key);
        }
 
        // removing an element
        void remove(int key)
        {
            // Applying hashFunc to find
            // index for given key
            int hash_val = HashFunc(key);
            hash_node entry = hashtable[hash_val];
            if (entry.key != key || entry == null) {
                System.out.println(
                    "Couldn't find any element at this key "
                    + key);
                return;
            }
 
            // if some values are present at that key &
            // traversing the list and removing all values
            while (entry != null) {
                if (entry.next == null) {
                    if (entry.prev == null) {
                        hashtable[hash_val] = null;
                        top[hash_val] = null;
                        break;
                    }
                    else {
                        top[hash_val] = entry.prev;
                        top[hash_val].next = null;
                        entry = top[hash_val];
                    }
                }
                entry = entry.next;
            }
            System.out.println(
                "Element was successfully removed at the key "
                + key);
        }
 
        // inserting method
        void add(int key, int value)
        {
            // Applying hashFunc to find
            // index for given key
            int hash_val = HashFunc(key);
            hash_node entry = hashtable[hash_val];
 
            // if key has no value stored
            if (entry == null) {
                // creating new node
                entry = new hash_node();
                entry.val = value;
                entry.key = key;
                entry.next = null;
                entry.prev = null;
                hashtable[hash_val] = entry;
                top[hash_val] = entry;
            }
 
            // if some values are present
            else {
                // traversing till the end of
                // the list
                while (entry != null)
                    entry = entry.next;
 
                // creating the new node
                entry = new hash_node();
                entry.val = value;
                entry.key = key;
                entry.next = null;
                entry.prev = top[hash_val];
                top[hash_val].next = entry;
                top[hash_val] = entry;
            }
            System.out.println(
                "Value " + value
                + " was successfully added at key " + key);
        }
    }
 
    // Driver Code
    public static void main(String[] args)
    {
 
        HashMap hash = new HashMap();
        hash.add(4, 5);
        hash.find(4);
        hash.remove(4);
    }
}
 
// This code is contributed by Lovely Jain

Value 5 was successfully added at key 4
Element found at key 4: 5
Element was successfully removed at the key 4