Hash Tables in C++ - Sanfoundry

This C++ Program demonstrates operations on Hash Tables

Here is source code of the C++ Program to demonstrate Hash Tables. 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
```
```
 */
```
```
#include<iostream>
```
```
#include<cstdlib>
```
```
#include<string>
```
```
#include<cstdio>
```
```
using namespace std;
```
```
const int TABLE_SIZE = 128;
```
```
 
```
```
/*
```
```
 * HashEntry Class Declaration
```
```
 */
```
```
class HashEntry
```
```
{
```
```
    public:
```
```
        int key;
```
```
        int value;
```
```
        HashEntry(int key, int value)
```
```
        {
```
```
            this->key = key;
```
```
            this->value = value;
```
```
        }
```
```
};
```
```
 
```
```
/*
```
```
 * HashMap Class Declaration
```
```
 */
```
```
class HashMap
```
```
{
```
```
    private:
```
```
        HashEntry **table;
```
```
    public:   
```
```
        HashMap()
```
```
	{
```

            table = new HashEntry * [TABLE_SIZE];

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

```
            {
```
```
                table[i] = NULL;
```
```
            }
```
```
        }
```
```
        /*
```
```
         * Hash Function
```
```
         */
```
```
        int HashFunc(int key)
```
```
        {
```
```
            return key % TABLE_SIZE;
```
```
        }
```
```
        /*
```
```
         * Insert Element at a key
```
```
         */
```
```
	void Insert(int key, int value)
```
```
	{
```
```
            int hash = HashFunc(key);
```

            while (table[hash] != NULL && table[hash]->key != key)

```
            {
```

                hash = HashFunc(hash + 1);

```
            }
```
```
            if (table[hash] != NULL)
```
```
                delete table[hash];
```

            table[hash] = new HashEntry(key, value);

```
	}
```
```
        /*
```
```
         * Search Element at a key
```
```
         */
```
```
        int Search(int key)
```
```
	{
```
```
	    int  hash = HashFunc(key);
```

	    while (table[hash] != NULL && table[hash]->key != key)

```
	    {
```
```
	        hash = HashFunc(hash + 1);
```
```
	    }
```
```
	    if (table[hash] == NULL)
```
```
	        return -1;
```
```
	    else
```
```
	        return table[hash]->value;
```
```
        }
```
```
 
```
```
        /*
```
```
         * Remove Element at a key
```
```
         */
```
```
        void Remove(int key)
```
```
	{
```
```
	    int hash = HashFunc(key);
```
```
	    while (table[hash] != NULL)
```
```
	    {
```
```
	        if (table[hash]->key == key)
```
```
	            break;
```
```
	        hash = HashFunc(hash + 1);
```
```
	    }
```
```
            if (table[hash] == NULL)
```
```
	    {
```

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

```
                return;
```
```
            }
```
```
            else
```
```
            {
```
```
                delete table[hash];
```
```
            }
```

            cout<<"Element Deleted"<<endl;

```
        }
```
```
        ~HashMap()
```
```
	{
```

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

```
            {
```
```
                if (table[i] != NULL)
```
```
                    delete table[i];
```
```
                delete[] table;
```
```
            }
```
```
        }
```
```
};
```
```
/*
```
```
 * 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.Search(key) == -1)
```
```
            {
```

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

```
	        continue;
```
```
	    }
```
```
	    else
```
```
	    {
```

	        cout<<"Element at key "<<key<<" : ";

```
	        cout<<hash.Search(key)<<endl;
```
```
	    }
```
```
            break;
```
```
        case 3:
```

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

```
            cin>>key;
```
```
            hash.Remove(key);
```
```
            break;
```
```
        case 4:
```
```
            exit(1);
```
```
        default:
```

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

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

$ g++ hash_table.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: 12
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: 24
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: 36
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: 48
Enter key at which element to be inserted: 4
 
----------------------
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: 60
Enter key at which element to be inserted: 5
 
----------------------
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: 3
Element at key 3 : 36
 
----------------------
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: 5
Element at key 5 : 60
 
----------------------
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: 4
Element 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: 4
No element found at key 4
 
----------------------
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
Element at key 2 : 24
 
----------------------
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