i am trying to make a Write a C++ program that has linked list the code i am using is given below but its showing some errors

aabiavvan (3)
#include<bits/stdc++.h>
using namespace std;
struct customer{
unsigned int sequence_number;
int month,day,year,hour,minute;
string name,service_required;
struct customer *next;
};
class task{

public:
struct customer *head,*last;

task()
{
head=last=NULL;
}
~task()
{
struct customer *start,*temp;
start=temp=head;
while(start!=NULL)
{
temp=start;
start=start->next;
free(temp);
}
}
void insert_node(string name,int day,int month,int year,int hour,int minute)
{ static int counter=0;
struct customer *node=NULL;

node = new struct customer();
node->name=name;
node->day=day;
node->month=month;
node->year=year;
node->hour=hour;
node->minute=minute;
node->sequence_number=counter++;
if(head==NULL && last==NULL)
{
head=last=node;
node->next=NULL;
}
else
{
node->next=head;
head=node;
}

}
int delete_node(string name)
{
struct customer *deleted,*start=head;
deleted=search(name,head);

if(deleted==NULL)
{
return 1;
}
else
{// cout<<deleted->name<<endl;
if(deleted!=head)
{
while(start->next!=deleted)
{
start=start->next;
}

start->next=deleted->next;
free(deleted);
}
else
{
head=deleted->next;
free(deleted);
}

return 0;
}
}

struct customer search(string name,struct customer start)
{
if(start==NULL)
return NULL;
else
{
if(name.compare(start->name)==0)
{
return start;
}
else
{
return search(name,start->next);

}
}
}

struct customer * serve_customer()
{
struct customer *start;
start=head;
while(start->next != last)
{
start=start->next;
}
free(start->next);
start->next = NULL;
return start;
}

void list_all(struct customer *start)
{
if(start==NULL)
return ;
list_all(start->next);
cout<<start->sequence_number<<" "<<start->name<<" "<<start->day<<"//"<<start->month<<" "<<start->year<<"//"<<start->hour<<"::"<<start->minute<<endl;
}


};
int main()
{
int choice,temp;
unsigned int sequence_number;
int month,day,year,hour,minute;
string name,service_required;
task object1;

while(1)
{ cout<<endl;
cout<<"Enter the choice\n";
cout<<"1) New customer arrival \n2) Serve Customer\n3) Customer left remove from waiting list\n4) List all customers waiting for service\n5) To exit";
cin>>choice;

switch(choice)
{
case 1:
cout<<"enter name\n";
cin>>name;
cout<<"Enter date as day,month,year\n";
cin>>day>>month>>year;
cout<<"Enter time as hour and minute\n";
cin>>hour>>minute;
object1.insert_node(name,day,month,year,hour,minute);
break;
case 2:
object1.serve_customer();
break;
case 3:
cout<<"enter the name of customer\n";
cin>>name;
temp=object1.delete_node(name);
(temp==1)?cout<<"Already Served":cout<<"Deleted";
break;
case 4:
object1.list_all(object1.head);
break;
case 5:
return 0;
break;

}
}
}
Ganado (6811)
The most obvious issue I see is that you are calling free() on objects you allocate by new. You're mixing C and C++ memory management, and it will end in your program exploding.

Call delete on what you new.

Also, use code formatting by adding [code] and [/code] around your code.
Last edited on
aabiavvan (3)
@Ganado i am new user kindly will you please do little modifications in this program so i can run it smoothly
dhayden (5798)
Here is your code, indented and with Ganado's suggested fix (basically I just replaced "free" with "delete" globally).

I have added "dmh" to the code that I changed. I also pointed out some bugs. The main problem is in serve_customer().
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#include<bits/stdc++.h>
using namespace std;
struct customer {
    unsigned int sequence_number;
    int month, day, year, hour, minute;
    string name, service_required;
    struct customer *next;
};

class task {
public:
    struct customer *head, *last;

    task()
    {
	head = last = NULL;
    }
     ~task()
    {
	struct customer *start, *temp;
	start = temp = head;
	while (start != NULL) {
	    temp = start;
	    start = start->next;
	    delete(temp);	// dmh
	}
    }
    void insert_node(string name, int day, int month, int year, int hour, int minute)
    {
	static int counter = 0;
	struct customer *node = NULL;

	node = new struct customer ();
	node->name = name;
	node->day = day;
	node->month = month;
	node->year = year;
	node->hour = hour;
	node->minute = minute;
	node->sequence_number = counter++;
	if (head == NULL && last == NULL) {
	    head = last = node;
	    node->next = NULL;
	} else {
	    node->next = head;
	    head = node;
	}

    }
    int delete_node(string name)
    {
	struct customer *deleted, *start = head;
	deleted = search(name, head);

	if (deleted == NULL) {
	    return 1;
	} else {				 // cout<<deleted->name<<endl;
	    if (deleted != head) {
		while (start->next != deleted) {
		    start = start->next;
		}

		start->next = deleted->next;
		delete (deleted); // dmh
	    } else {
		head = deleted->next;
		delete (deleted); // dmh
	    }

	    return 0;
	}
    }

    // dmh: The "start" parameter is a pointer and it returns a pointer
    struct customer *search(string name, struct customer *start)
    {
	if (start == NULL)
	    return NULL;
	else {
	    if (name.compare(start->name) == 0) {
		return start;
	    } else {
		return search(name, start->next);
	    }
	}
    }

    struct customer *serve_customer()
    {
	struct customer *start;
	start = head;
	// dmh - it looks like you're trying to delete the last node.
	// There are three bugs here. First, it won't work if the list
	// is empty.  Second, it doesn't update last. Third, if it
	// deletes the last item, it needs to update head as well as
	// last.
	while (start->next != last) {
	    start = start->next;
	}
	delete (start->next);	// dmh
	start->next = NULL;
	return start;
    }

    void list_all(struct customer *start)
    {
	if (start == NULL)
	    return;
	list_all(start->next);
	cout << start->sequence_number << " " << start->name << " " << start->
	    day << "//" << start->month << " " << start->year << "//" << start->
	    hour << "::" << start->minute << endl;
    }

};

int
main()
{
    int choice, temp;
    unsigned int sequence_number;
    int month, day, year, hour, minute;
    string name, service_required;
    task object1;

    while (1) {
	cout << endl;
	cout << "Enter the choice\n";
	cout <<
	    "1) New customer arrival \n2) Serve Customer\n3) Customer left remove from waiting list\n4) List all customers waiting for service\n5) To exit";
	cin >> choice;

	switch (choice) {
	case 1:
	    cout << "enter name\n";
	    cin >> name;
	    cout << "Enter date as day,month,year\n";
	    // dmh = the line below only works of the day, month and
	    // year are separated by spaces (or tabs, newlines etc).
	    // But the instructions above indicate that they should be
	    // separated by commas.  So if the user enters
	    // "23,10,2019" then the code will read "23,10,2019" into
	    // "day" and then wait for more input for month and year
	    cin >> day >> month >> year;
	    cout << "Enter time as hour and minute\n";
	    cin >> hour >> minute;
	    object1.insert_node(name, day, month, year, hour, minute);
	    break;
	case 2:
	    object1.serve_customer();
	    break;
	case 3:
	    cout << "enter the name of customer\n";
	    cin >> name;
	    temp = object1.delete_node(name);
	    (temp == 1) ? cout << "Already Served" : cout << "Deleted";
	    break;
	case 4:
	    object1.list_all(object1.head);
	    break;
	case 5:
	    return 0;
	    break;

	}
    }
}

aabiavvan (3)
thanks sir really appreciated.
may ALLAH bless you
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