segmenation error

Question

#include<iostream>

#include<string>

using namespace std;

struct employee

{

int age,year;

string name;

employee *next;

};

class List

{

private:

employee *head,*temp;

public:

List()

{

head = NULL;

}

/* void insert()

{

string name_Array[7]= {"Javeria","Nageeta","Karishma","Bakhtawar","Malook","Shakeel","Nadir"};

int age_Array[7] = {105,95,115,19,15,10,18};

int year_Array[7] = {1987,1990,2011,2015,2017,2019,2019};

employee *temp = head;

for(int i=0; i<7; i++)

{

employee *newNode = new employee;

newNode->name = name_Array[i];

newNode->age = age_Array[i];

newNode->year = year_Array[i];

newNode->next = NULL;

temp->next = newNode;

temp = temp->next;

    if(i==0)

    {

    temp = newNode;

head = newNode;

}

else

{

temp->next = newNode;

temp = temp->next;

}   

}

}*/

void insert(string name, int age, int year)

{

employee *newNode,*current = head, *previous = NULL;

newNode = new employee;

newNode->name = name;

newNode->age = age;

newNode->year = year;

newNode->next = NULL;

if(head == NULL)

{

head = newNode;

current = newNode;

previous = NULL;

}

else

{

current = head;

while(current!=NULL)

{

previous = current;

current = current->next;

if(current->year >= previous->year)

{

previous->next = current->next;

//current = current->next;

}

else

{

}

}

}

}

//=======================================================

/* void display()

    {

    for(employee* p = head; p != NULL; p = p->next)

    {

        cout<<p->name<<endl;

        cout<<p->age<<endl;

        cout<<p->year<<endl;

    }

    

*/ }

//=======================================================

void display_N()

{

temp = head;

int i=0;

while(temp!=NULL)

{

i++;

cout<<temp->name<<" ";

        cout<<temp->age<<" ";

        cout<<temp->year<<endl;

        temp = temp->next;

cout<<"in while loop "<<i<<endl;

}

}

//===================================================

};

int main()

{

string name;

int age,year;

List *obj = new List;

for(int i=0; i<3; i++)

{

cout<<"Enter Name of employee : ";

getline(cin,name);

cout<<"Enter age of employee : ";

cin>>age;

cout<<"Enter year of employee : ";

cin>>year;

cin.ignore();

obj->insert(name,age,year);

}

obj->display_N();

/*obj->display();*/

return 0;

}

Answer 1

go on google and search! easy!

Answer 2

Your insert function has current incremented in the loop and current could become nullptr and dereferenced (previous->next = current->next;), causing the segmentation fault.

I've fixed up your code and ended up with this. You should write a destructor that frees up all the allocated memory though!

#include <iostream>
#include <string>

using namespace std;

struct employee
{
    int age, year;
    string name;
    employee * next;
};

class List
{
private:
    employee * head;

public:
    List()
    {
        head = nullptr;
    }
    
    void insert(string name, int age, int year)
    {
        // Create the new node
        employee * newNode = new employee { age, year, name, nullptr };
        
        // Find the where to insert the new node
        employee * insertAfter = nullptr;
        for (employee * current = head; current != nullptr; current = current->next)
        {
            if (current->year <= newNode->year)
            {
                insertAfter = current;
            }
            else
            {
                break;
            }
        }
        
        // Insert the new node
        if (insertAfter == nullptr) // The node goes to the head of the list
        {
            newNode->next = head;
            head = newNode;
        }
        else // The node goes inside the list
        {
            newNode->next = insertAfter->next;
            insertAfter->next = newNode;
        }
    }

    void display()
    {
        for (employee * temp = head; temp != nullptr; temp = temp->next)
        {
            cout << temp->name << " ";
            cout << temp->age << " ";
            cout << temp->year << endl;
        }
    }
};

int main()
{
    string name;
    int age, year;
    List *obj = new List;
    for (int i = 0; i < 3; i++)
    {
        cout << "Enter name of employee : ";
        getline(cin, name);
        cout << "Enter age of employee : ";
        cin >> age;
        cout << "Enter year of employee : ";
        cin >> year;
        cin.ignore();
        obj->insert(name, age, year);
    }
    obj->display();
    return 0;
}