 //Consider telephone book database of N clients. 
//Make use of a hash table implementation to quickly look up client‘s telephone number.

#include<iostream>

using namespace std;

struct node
{
    int value;
    node* next;

}*HashTable[10];

class hashing
{
    public:

    hashing()
    {

        for(int i=0 ; i<10 ; i++){
            HashTable[i]=NULL;
        }
    }


    int HashFunction(int value)
    {
        return (value%10);
    }

    node* create_node(int x)
    {
        node* temp=new node;
        temp->next=NULL;
        temp->value=x;
        return temp;
    }

    void display()
    {
        for(int i=0 ; i< 10; i++)
        {
            node * temp=new node;
            temp=HashTable[i];
            cout<<"a["<<i<<"] : ";
            while(temp !=NULL)
            {
                cout<<" ->"<<temp->value;
                temp=temp->next;
            }
            cout<<"\n";
        }
    }    

    int searchElement(int value)
    {
        bool flag = false;
        int hash_val = HashFunction(value);
        node* entry = HashTable[hash_val];
        cout<<"\nElement found at : ";
        while (entry != NULL)
        {
            if (entry->value==value)
            {
                cout<<hash_val<<" : "<<entry->value<<endl;
                flag = true;
            }
            entry = entry->next;
        }
        if (!flag)
            return -1;
    }

    void deleteElement(int value)
    {
        
        int hash_val = HashFunction(value);
        node* entry = HashTable[hash_val];

        if (entry == NULL )
        {
            cout<<"No Element found ";
            return;
        }

        if(entry->value==value){
            HashTable[hash_val]=entry->next;
            return;
        }
        while ((entry->next)->value != value)
        {
            entry = entry->next;
        }
        entry->next=(entry->next)->next;
    }

    void insertElement(int value)
    {
        
        int hash_val = HashFunction(value);
        // node* prev = NULL;
        //node* entry = HashTable[hash_val];
        node* temp=new node;
        node* head=new node;
        head = create_node(value);
        temp=HashTable[hash_val];
        if (temp == NULL)
        {
            HashTable[hash_val] =head;
        }
        else
        {
            while (temp->next != NULL)
            {
                temp = temp->next;
            }
            temp->next =head;

        }
    }
};

int main(){
    int ch;
    int data,search,del;
    hashing h;
    do{
        cout<<"\nTelephone : \n1.Insert \n2.Display \n3.Search \n4.Delete \n5.Exit \n\n OPTION: ";
        cin>>ch;
        switch(ch)
        {
            case 1:
                cout<<"\nEnter phone no. to be inserted : ";
                cin>>data;
                h.insertElement(data);
                break;
            case 2:
                h.display();
                break;
            case 3:
                cout<<"\nEnter the no to be searched : ";
                cin>>search;

                if (h.searchElement(search) == -1)
                {
                    cout<<"No element found at key ";
                    continue;
                }
                break;
            case 4:
                cout<<"\nEnter the phno. to be deleted : ";
                cin>>del;
                h.deleteElement(del);
                cout<<"Phno. Deleted"<<endl;
                break;
        }
    }while(ch!=5);
    
    return 0;
}

created 3 years ago by Jayant Sonkusare

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About C++

C++ is a widely used middle-level programming language.

Supports different platforms like Windows, various Linux flavours, MacOS etc
C++ supports OOPS concepts like Inheritance, Polymorphism, Encapsulation and Abstraction.
Case-sensitive
C++ is a compiler based language
C++ supports structured programming language
C++ provides alot of inbuilt functions and also supports dynamic memory allocation.
Like C, C++ also allows you to play with memory using Pointers.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition If-Else is used.

if(conditional-expression) {
   //code
}
else {
   //code
}

You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to If-Else-If ladder.

switch(conditional-expression){    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
......    
    
default:     
 code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  //code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while (condition) {  
// code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {  
 // code 
} while (condition);

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity. Function gets run only when it is called.

How to declare a Function:

return_type function_name(parameters);

How to call a Function:

function_name (parameters)

How to define a Function:

return_type function_name(parameters) {  
 // code
}