LINKED LIST double

#include<stdio.h>
#include<stdlib.h>

typedef struct Data
{
    int a;
    struct Data *next;
    struct Data *prev;
} Data;

Data *head=NULL;
Data *tail=NULL;

void insert_at_first(int x)
{
    Data *new_node  = (Data*)malloc(sizeof(Data));

    new_node -> a = x;
    new_node -> next = NULL;
     new_node -> prev = NULL;

    if(head == NULL)
    {
        head = new_node;
        tail = new_node;
        return;
    }

    new_node -> next = head;
   new_node -> prev = NULL;
    head = new_node;
}

void insert_at_end(int x)
{
    Data *new_node  = (Data*)malloc(sizeof(Data));

    new_node -> a = x;

    new_node -> next = NULL;
 new_node -> prev = NULL;
    if(head==NULL)
    {
        head=new_node;
        tail=new_node;
        return;
    }
    new_node->prev=tail;
    tail -> next = new_node;
tail=new_node;
}
void insert_at_nth(int n,int x)
{
    Data *newnode=(Data*)malloc(sizeof(Data));
    newnode->a=x;
    newnode->next=NULL;
    Data *temp=head;

    if(head == NULL || n == 1)
    {
        newnode -> next = head;
        head->prev = newnode;
        head = newnode;
        tail=newnode;
        return;
    }

    n=n-2;

    while(n-- && temp -> next != NULL)
    {
        temp=temp->next;
    }

    newnode->next=temp->next;
    temp->next->prev=newnode;
    newnode->prev=temp;
    temp->next=newnode;
}


void del_by_pos(int n)
{
    Data *temp=head;

    if(n==1)
    {
        head = temp -> next;
        head -> prev = NULL;
        free(temp);
        return;
    }
    else
    {
        n=n-2;
        while(n-- && temp != NULL)
        {
            temp=temp -> next;
        }
        Data *del= temp -> next;
        temp -> next = del-> next;
        del -> prev = temp;
        free(del);
        temp = head;
        while(temp != NULL)
        {
            printf("%d ", temp -> a);
            temp = temp -> next;
        }
        printf("\n");
    }
}

int count()
{
    int cnt=0;
    Data *temp = head;
    while(temp != NULL)
    {
        temp = temp -> next;
        ++cnt;
    }
    printf("Total nodes %d\n",cnt);
    return cnt;
}
int Add()
{
    int sum=0;
    Data *temp = head;
    sum = temp -> a;
    while(temp -> next != NULL)
    {
        temp = temp -> next;
        sum = sum + temp -> a;
    }
    printf("Total sum %d\n",sum);
    return sum;
}
void search(int x)
{
    int c=0;
    Data *temp = head;
    while(temp != NULL)
    {
        if (temp -> a == x)
        {
            ++c;
        }
        temp = temp -> next;
    }
    if (c>0)
    {
        printf("Match Found\n");
    }
    else
        printf("Match Not Found\n");
}
void Avr()
{
    float av;
    int sum=0,cnt=0;
    Data *temp = head;
    sum = temp -> a;
    while(temp -> next != NULL)
    {
        temp = temp -> next;
        sum = sum + temp -> a;
        ++cnt;
    }

    av = ((sum*1.00)/(cnt*1.00));
    printf ("Average %.2lf\n",av);
}

void Print()
{
    Data *temp = head;

    while(temp != NULL)
    {
        printf("%d ", temp -> a);
        temp = temp -> next;
    }
    printf("\n");
}

int main()
{

    insert_at_end(6);
    insert_at_first(5);
    insert_at_first(4);
    insert_at_first(3);
    insert_at_end(6);
    insert_at_end(7);
    Print();
    count();
    Add();
    search(3);
    Avr();
    del_by_pos(2);
}