Process returned -1073741819 (0xC0000005) error - c++

Question

I'm a beginner in coding. I am woring on a mini project to write a car parking system from my college. I used doubly-linked list to insert, search and delete to add, search and remove cars in the system .In this program, everything works fine untill i compile the program to remove a Car.Whenever i enter the car number to remove it from parking the error occurs and the carparking.exe suddenly stops.
This is my program:
#include <iostream>
using namespace std;
struct node
{
int no;
int charge,entry_time,exit_time;
char name[20];
node *prev, *next;
};
class Car
{
private:
node *head;
char ch[20];
public:
Car()
{
head= NULL;
}
void input()
{
cout<<"\nWelcome to Car Parking system\n"<<endl;
cout<<"\n Press 1: To Park a Car"<<endl;
cout<<"\n Press 2: To Search a Car"<<endl;
cout<<"\n Press 3: To Remove of Car"<<endl;
cout<<"\n Press 4: To display the Parking records"<<endl;
cout<<"\n Press 5: Exit the program"<<endl;
return;
}
void add_car()
{
node *newer= new node;
system("cls");
cout<<"Enter the Car number: "<<endl;
cin>>newer->no;
fflush(stdin);
cout<<"Enter the name of driver: "<<endl;
cin.getline(newer->name,20);
fflush(stdin);
cout<<"Enter the entry time of car"<<endl;
cin>>newer->entry_time;
fflush(stdin);
cout<<"Enter the exit time of car"<<endl;
cin>>newer->exit_time;
fflush(stdin);
newer->charge=(newer->exit_time-newer->entry_time)*300;
newer->next =head;
newer->prev =NULL;
if(head!=NULL)
{
head->prev = newer;
}
head= newer;
cout<<"\nThe car is parked successfully"<<endl;
if(head==NULL)
{
cout<<"\n No Car is parked: "<<endl;
}
}
void del_car()
{
if(head==NULL)
{
cout<<"\n No Car is parked "<<endl;
}
else
{
int value;
cout<<"\nEnter the Car number to move"<<endl;
cin>>value;
node *temp=head;
bool flag=false;
if(temp->no== value)
{
head=temp->next;
head->prev=NULL;
flag= true;
delete temp;
if(flag==true)
{
cout<<"\nThe Parking charge is Rs "<<temp->charge<<" only"<<endl;
cout<<"The car is moved out of parking zone"<<endl;
}
}
else
{
while (temp!=NULL)
{
if(temp->no==value)
{
node *p,*q;
if(temp->next==NULL)
{
p=temp->prev;
p->next=NULL;
flag=true;
delete temp;
}
else
{
p=temp->prev;
q=temp->next;
p->next=q;
q->prev=p;
flag=true;
delete temp;
}
}
temp=temp->next;
}
if(flag==false)
{
cout<<"\n\t The car number is not found"<<endl;
}
}
}
}
void display()
{
if(head==NULL)
{
cout<<"No Car is parked"<<endl;
}
else
{
node *temp= head;
while(temp!= NULL)
{
cout<<"\n------------------------------Information----------------------------------------"<<endl;
cout<<"\n\tThe name of the driver is:"<<temp->name<<endl;
cout<<"\n\tThe Car number is: "<<temp->no<<endl;
cout<<"\n\tThe entry time of the car is: "<<temp->entry_time<<endl;
cout<<"\n\tThe exit time of the car is: "<<temp->exit_time<<endl;
temp =temp->next;
}
}
}
void search()
{
if(head==NULL)
{
cout<<"No Car is parked"<<endl;
}
else
{
int value;
cout<<"\nEnter the car number to search"<<endl;
cin>>value;
node *temp=head;
bool flag=false;
if(temp->no=value)
{
cout<<"\n\t----Information of the Car-----"<<endl;
cout<<"\nThe name of the driver is: "<<temp->name<<endl;
cout<<"\nThe Car number is: "<<temp->no<<endl;
cout<<"\nThe entry time is: "<<temp->entry_time<<endl;
cout<<"\nThe Car is still Parked "<<endl;
cout<<"\nThe Parking charge is still pending "<<endl;
return;
}
temp= temp->next;
}
}
};
int main()
{
int n;
string ch;
Car c1;
x2:
c1.input();
cout<<"\n\t----Enter your choice----"<<endl;
cin>>n;
if(n==1)
{
x1:
c1.add_car();
cout<<"\nDo you want to go to Main Menu: Press(y or n)"<<endl;
cin>>ch;
fflush(stdin);
if(ch=="Y" || ch=="y")
{
goto x2;
}
else
{
exit(1);
}
}
else if(n==2)
{
c1.search();
cout<<"\nDo you want to go to Main Menu: Press(y or n)"<<endl;
cin>>ch;
if(ch=="Y"||ch=="y")
{
goto x2;
}
else
{
exit(1);
}
}
else if(n==3)
{
c1.del_car();
cout<<"\nDo you want to go to Main Menu: Press(y or n)"<<endl;
cin>>ch;
if(ch=="Y"||ch=="y")
{
goto x2;
}
else
{
exit(1);
}
}
else if(n==4)
{
c1.display();
cout<<"\nDo you want to go to Main Menu: Press(y or n)"<<endl;
cin>>ch;
if(ch=="Y"||ch=="y")
{
goto x2;
}
else
{
exit(1);
}
}
else if(n==5)
{
exit(1);
}
else
{
cout<<"\n\tChoose correct number"<<endl;
goto x2;
}
return 0;
}

Answer 1

In the function del_car()
if(temp->no== value)
{
head=temp->next;
head->prev=NULL;
}
If there is only car parked, then only head is valid and head->next and head->prev will be NULL. Now,
head = temp->next; // head becomes NULL here
head->prev = NULL; //you are dereferencing a NULL pointer and hence the seg. fault
Just setting head = NULL should do in this condition.
Also, if there are more cars parked, the condition is while(temp!=NULL), but if the car is found, then you have to break the loop so that temp won't be incremented unnecessarily. Add a break; after flag=true;.