problem

[max v max2]

why this is not working ?

  #include<iostream>
using namespace std;
struct node {
	node *prev;
	int data;
	node *next;
};


void add(node **head,node **tail,int x)
{
	node *loc=*head;
	node *ptr=new node;
	ptr->data=x;
	ptr->next=NULL;
	ptr->prev=NULL;
	int count=0;
	if(*head==NULL)
	{
		*head=*tail=ptr;
	}
	
	else
	{
		node *cur;
		for(cur=*head;cur!=NULL;cur=cur->next)
			count++;
		cur=*head;

		for(int i=0;i<count/2;i++)
			cur=cur->next;
	

		for(node *cur=*head;cur!=NULL;cur=cur->next)
			count++;

		
		ptr->next=cur->next;
		ptr->prev=cur;
		(cur->next)->prev=ptr;
		cur->next=ptr;
	}
}

void print (node *head,node *tail)
{
	if(tail!=NULL)
		for(node *loc=tail;loc!=NULL;loc=loc->prev)
			cout<<loc->data<<" ";
}

int main()
{
	int x,y;
	node *head,*tail;
	do{
		system("cls");
		cout<<"1.Insert at the middle of the list\n"
			<<"2.Delete the second half of the list\n"
			<<"3.Print the list\n"
			<<"4.Exit\n"
			<<"Enter Your Choice : ";
		cin>>x;
		switch(x)
		{
		case 1 :{
			cout<<"please enter a number to add"<<endl;
			cin>>y;
			add(&head,&tail,y);
				}break;
		
		case 3:print(head,tail);
			break;
		case 4:cout<<"Bye Bye"<<endl;
			break;
		default :cout<<"invaild input"<<endl;
		}
	}while(x!=4);
	system("pause");
	return 0;
}

[Peter87]

You have forgot to initialize head and tail.

[max v max2]

Thank you , i really don't notice that.