how to add node in between in a linked list

[cshingk]

Hi, i am new in linked list, and now i face a problem on how to add the node into middle of a list. Example like if i got a name list show below:

1.andrew
2.eric
3.madness
4.gerik

Now how can i put 'gerik' in the middle that is below eric and above madness.

Below will be my example code, please help me thank by giving me advise or code sample:

#include <iostream>
#include <string>
#include <cstdlib>
#include <cstring>

using namespace std;

struct node
{
    char f_name[20];
    char l_name[20];
    char u_id[10];
    node *next;
};

node *head;
node *curr;

//prototype
void display();
void add();
void search_name();
void insert_data(node *tempnode);
void insert_before_head(node *tempnode);
void menu(char choice);
char pause;

//function start...
void search_name()
{
    char name[20];
    curr = head;
    cin.ignore(30,'\n');
    cout<<"Key In Last Name :"<<endl;
    cin.get(name, 20);
    cin.ignore(30,'\n');

    while((curr->next != NULL) && (strcmp(curr->l_name, name) != 0))
    {
        curr = curr->next;
    }
    if(curr != NULL)
    {
        cout<<"Record Found !"<<endl;
        cout<<"First Name"<<setw(16)<<"Last Name"<<setw(16)<<"User ID"<<endl;
        cout<<"--------------------------------------------------------------"<<endl;
        cout<<curr->f_name<<setw(20)<<curr->l_name<<setw(16)<<curr->u_id<<endl<<endl;

    }
    else
    {
        cout<<"No Match !"<<endl;
        cout<<"Press 'Enter' To Continue"<<endl;
        cin.get(pause = getch());
        system("cls");
    }
};
void display()
{
    curr = head;
    if(head != NULL)
    {
        cout<<"First Name"<<setw(16)<<"Last Name"<<setw(16)<<"User ID"<<endl;
        cout<<"--------------------------------------------------------------"<<endl;
        while(curr != NULL)
        {
            cout<<curr->f_name<<setw(20)<<curr->l_name<<setw(16)<<curr->u_id<<endl;
            curr = curr->next;
        }
    }
    else
    {
        cout<<"No Data. File storage Empty!"<<endl;
    }
};
void add()
{
    node *temp;
    temp = new node;
    cin.ignore(30, '\n');
    cout<<"Key In First Name:"<<endl;
    cin.get(temp->f_name, 20);
    cin.ignore(30, '\n');
    cout<<"Key In Last Name:"<<endl;
    cin.get(temp->l_name, 20);
    cin.ignore(30, '\n');
    cout<<"Key In Your ID:"<<endl;
    cin.get(temp->u_id, 10);
    insert_data(temp);
};

void insert_data(node *tempnode)
{
    node *temp;

    if(head == NULL)
    {
        node *temp;
        temp = new node;
        temp = head;
        tempnode->next = NULL;
        head = tempnode;
    }
    else if(strcmp(tempnode->l_name, head->l_name) < 0)
    {
            insert_before_head(tempnode);
    }
    else
    {
        temp = new node;
        curr = head;

        while(curr->next != NULL)
        {
            curr = curr->next;
        }
            temp = tempnode;
            curr->next = tempnode;
            tempnode->next = NULL;
    }

};
void insert_before_head(node *tempnode)
{
    node *temp;

    if(head != NULL)
    {
       temp = new node;
       temp = tempnode;
       tempnode->next = head;
       head = tempnode;
    }
};

void menu(int choice)
{
    switch (choice)
    {
    case 1 :
        add();
        break;
    case 2:
        display();
        break;
    case 3:
        search_name();
        break;
    case 4:
        cout<<"Exit Program !"<<endl;
        break;
    default :
        cout<<"Error! Program Terminate !"<<endl;
    }
};

int main()
{
    int choice;
    node *temp;
    head = NULL;
    curr = NULL;

    cout << "Data Stack Head And Any Position !" << endl;
    system("cls");
    do{
            cout<<"1. Add Data."<<endl;
            cout<<"2. Show Data. "<<endl;
            cout<<"3. Search Last Name "<<endl;
            cout<<"4. Exit. "<<endl;
            cin >>choice;
            menu(choice);

       }while(choice != 4);

 return 0;
}

[koothkeeper]

Please wrap your code in code tags: You can find them under Format:

Also, whenever you allocate memory, always check for failure. I'm referring to:

"temp = new node".

You are already sorting your list as you input your data, so you shouldn't have this problem.
Are you saying that your list isn't sorted?

[cshingk]

hi koothkeeper, my problem is when i add data one by one just like below sequence:

1.andrew
2.eric
3.madness
4.gerik

I want my data "gerik" in "madness" place when it show out. I am able to sort the data infront of "eric" but after "eric" i am not idea. I want my output just like:

1.andrew
2.eric
3.gerik
4.madness

thk.

[koothkeeper]

You do realize that your program only sorts on last name, right?

[cshingk]

Yah. so any idea on it?

[Momothegreat]

Oh if you know the size of the array, let's say "n", then the middle position would be "n-1/2". The last position would be n-1. So if want to swap the middle and last position, you can do so by creating a temporary variable to hold the position and then interchange them-- probably in a for loop.

[D80DSL3A]

I guess the thread died.
Another pointless post...

[anup30]

#include <iostream>
using namespace std;

struct List{
	List(string s="") : name(s){}
	string name;
	List *next= NULL;
};

int main() {
	List *head = new List("first");
	head->next = new List("second");
	head->next->next = new List("third");
	head->next->next->next = new List("fourth");	
	head->next->next->next->next = new List("fifth");	
		
	List *p1= head, *p2= head;
	for(int i=0; i<2; i++) p1 = p1->next;
	for(int i=0; i<4; i++) p2 = p2->next;	
	
	// swap p1 and p2 name
	List temp;
	temp.name = p1->name;
	p1->name = p2->name;
	p2->name = temp.name;	
	
	// print
	List *cur = head;
	while(cur != NULL){
		cout << cur->name << "\n";
		cur = cur->next;
	}

return 0;	
}

[koothkeeper]

@cshingk I am assuming you are showing a list of First names, not Last names.

If so, you must change your sort to sort on First name.