C++ Program to Implement Hash Tables Chaining with List Heads

This C++ Program demonstrates operations on Hash Tables Chaining with List Heads.

Here is source code of the C++ Program to demonstrate Hash Tables Chaining with List Heads. The C++ program is successfully compiled and run on a Linux system. The program output is also shown below.

```
/*
```

 * C++ Program to Implement Hash Tables Chaining with List Heads

```
 */
```
```
#include <iostream>
```
```
#include <cstdio>
```
```
#include <cstring>
```
```
#include <algorithm>
```
```
#include <cmath>
```
```
#include <vector>
```
```
#include <cstdlib>
```
```
using namespace std;
```
```
const int TABLE_SIZE = 5;
```
```
/*
```
```
 * Link List Class Declaration
```
```
 */
```
```
class LinkedHash
```
```
{
```
```
	public:
```
```
        int key, value;
```
```
        LinkedHash *next;
```
```
        LinkedHash(int key, int value)
```
```
        {
```
```
            this->key = key;
```
```
            this->value = value;
```
```
            this->next = NULL;
```
```
        }
```
```
};
```
```
/*
```
```
 * HashMap Class Declaration
```
```
 */
```
```
class HashMap
```
```
{
```
```
    private:
```
```
        LinkedHash **htable;
```
```
    public:
```
```
        HashMap()
```
```
        {
```

            htable = new LinkedHash*[TABLE_SIZE];

            for (int i = 0; i < TABLE_SIZE; i++)

```
            {
```
```
                htable[i] = NULL;
```
```
            }
```
```
        }
```
```
        ~HashMap()
```
```
        {
```

            for (int i = 0; i < TABLE_SIZE; i++)

```
            {
```
```
                if (htable[i] != NULL)
```
```
                {
```

                    LinkedHash *prev = NULL;

                    LinkedHash *entry = htable[i];

                    while (entry != NULL)

```
                    {
```
```
                        prev = entry;
```

                        entry = entry->next;

```
                        delete prev;
```
```
                    }
```
```
                }
```
```
                delete[] htable;
```
```
            }
```
```
        }
```
```
        /*
```
```
	     * Hash Function
```
```
         */
```
```
        int HashFunc(int key)
```
```
		{
```
```
            return key % TABLE_SIZE;
```
```
        }
```
```
        /*
```
```
	     * Insert Element at a key
```
```
         */
```
```
        void Insert(int key, int value)
```
```
        {
```

            int hash_val = HashFunc(key);

            if (htable[hash_val] == NULL)

                htable[hash_val] = new LinkedHash(key, value);

```
            else
```
```
            {
```

                LinkedHash *entry = htable[hash_val];

                while (entry->next != NULL)

                    entry = entry->next;

                    if (entry->key == key)

                        entry->value = value;

```
                    else
```

                        entry->next = new LinkedHash(key, value);

```
            }
```
```
        }
```
```
        /*
```
```
	     * Search Element at a key
```
```
         */
```
```
        int Find(int key)
```
```
        {
```

            int hash_val = HashFunc(key);

            if (htable[hash_val] == NULL)

```
                return -1;
```
```
            else
```
```
            {
```

                LinkedHash *entry = htable[hash_val];

                while (entry != NULL && entry->key != key)

                    entry = entry->next;

```
                if (entry == NULL)
```
```
                    return -1;
```
```
                else
```

                    return entry->value;

```
            }
```
```
        }
```
```
        /*
```
```
	     * Delete Element at a key
```
```
         */
```
```
        void Delete(int key)
```
```
        {
```

            int hash_val = HashFunc(key);

            if (htable[hash_val] != NULL)

```
            {
```

                LinkedHash *entry = htable[hash_val];

                LinkedHash *prev = NULL;

                while (entry->next != NULL && entry->key != key)

```
                {
```
```
                    prev = entry;
```

                    entry = entry->next;

```
                }
```
```
                if (entry->key == key)
```
```
                {
```
```
                    if (prev == NULL)
```
```
                    {
```

                        LinkedHash *next = entry->next;

```
                        delete entry;
```

                        htable[hash_val] = next;

```
                    }
```
```
                    else
```
```
                    {
```

                        LinkedHash *next = entry->next;

```
                        delete entry;
```

                        prev->next = next;

```
                    }
```
```
                }
```
```
            }
```
```
        }
```
```
};
```
```
/*
```
```
 * Main Contains Menu
```
```
 */
```
```
int main()
```
```
{
```
```
    HashMap hash;
```
```
    int key, value;
```
```
    int choice;
```
```
    while(1)
```
```
    {
```

        cout<<"\n----------------------"<<endl;

        cout<<"Operations on Hash Table"<<endl;

        cout<<"\n----------------------"<<endl;

        cout<<"1.Insert element into the table"<<endl;

        cout<<"2.Search element from the key"<<endl;

        cout<<"3.Delete element at a key"<<endl;

```
        cout<<"4.Exit"<<endl;
```
```
        cout<<"Enter your choice: ";
```
```
        cin>>choice;
```
```
        switch(choice)
```
```
        {
```
```
        case 1:
```

            cout<<"Enter element to be inserted: ";

```
            cin>>value;
```

            cout<<"Enter key at which element to be inserted: ";

```
            cin>>key;
```
```
            hash.Insert(key, value);
```
```
            break;
```
```
        case 2:
```

            cout<<"Enter key of the element to be searched: ";

```
            cin>>key;
```
```
            if (hash.Find(key) == -1)
```

            cout<<"No element found at key "<<key<<endl;

```
            else
```
```
            {
```

                cout<<"Elements at key "<<key<<" : ";

                cout<<hash.Find(key)<<endl;

```
            }
```
```
            break;
```
```
        case 3:
```

            cout<<"Enter key of the element to be deleted: ";

```
            cin>>key;
```
```
            if (hash.Find(key) == -1)
```

                cout<<"Key "<<key<<" is empty, nothing to delete"<<endl;

```
            else
```
```
            {
```
```
                hash.Delete(key);
```

                cout<<"Entry Deleted"<<endl;

```
            }
```
```
            break;
```
```
        case 4:
```
```
            exit(1);
```
```
        default:
```

           cout<<"\nEnter correct option\n";

```
       }
```
```
    }
```
```
    return 0;
```
```
}
```

$ g++ hash_listheads.cpp
$ a.out
 
----------------------
Operations on Hash Table
 
----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 1
Enter element to be inserted: 100
Enter key at which element to be inserted: 1
 
----------------------
Operations on Hash Table
 
----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 1
Enter element to be inserted: 200
Enter key at which element to be inserted: 2
 
----------------------
Operations on Hash Table
 
----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 1
Enter element to be inserted: 300
Enter key at which element to be inserted: 3
 
----------------------
Operations on Hash Table
 
----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 1
Enter element to be inserted: 600
Enter key at which element to be inserted: 6
 
----------------------
Operations on Hash Table
 
----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 1
Enter element to be inserted: 700
Enter key at which element to be inserted: 7
 
----------------------
Operations on Hash Table
 
----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 1
Enter element to be inserted: 800
Enter key at which element to be inserted: 8
 
----------------------
Operations on Hash Table
 
----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 2
Enter key of the element to be searched: 2
Elements at key 2 : 200
 
----------------------
Operations on Hash Table
 
----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 2
Enter key of the element to be searched: 7
Elements at key 7 : 700
 
----------------------
Operations on Hash Table
 
----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 2
Enter key of the element to be searched: 9
No element found at key 9
 
----------------------
Operations on Hash Table
 
----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 3
Enter key of the element to be deleted: 7
Entry Deleted
 
----------------------
Operations on Hash Table
 
----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 2
Enter key of the element to be searched: 7
No element found at key 7
 
----------------------
Operations on Hash Table
 
----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 2
Enter key of the element to be searched: 2
Elements at key 2 : 200
 
----------------------
Operations on Hash Table
 
----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 1
Enter element to be inserted: 1111
Enter key at which element to be inserted: 7
 
----------------------
Operations on Hash Table
 
----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 2
Enter key of the element to be searched: 7
Elements at key 7 : 1111
 
----------------------
Operations on Hash Table
 
----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 4
 
------------------
(program exited with code: 1)
Press return to continue

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