C++ - No matching function to call to

I am making a singly linked list :

#include <conio.h>
#include <iostream>
#include <stdlib.h>

using namespace std;

struct node
{
    int a;
    struct node *ptr;
};

node::node(int p) : {}

struct node *head;

void create(int d)
{
    if(head==NULL)
    {
        head->a=d;
        head->ptr=NULL;
    }
    else
    {
        struct node* temp =(struct node*) malloc(sizeof(struct node));
        temp=head;
        while(temp==NULL)
            temp=temp->ptr;
        temp->a=d;
        temp->ptr=NULL;
    }

}

void display()
{
    struct node* temp =(struct node) malloc(sizeof(struct node));
    temp=head;
    while(temp==NULL)
    {
        cout<<temp->a<<" --> ";
        temp=temp->ptr;
    }
    cout<<endl;
}

int main()
{
    head=NULL;
    create(5);
    create(6);
    create(8);
    display();
    return 0;
}

I am getting this error when I try to compile it:

..\linkedlist.cpp: In function 'void display()':
..\CPP\linkedlist.cpp:36:61: error: no matching function for call to 'node::node(void*)'
..\CPP\linkedlist.cpp:8:1: note: candidates are: node::node()
..\CPP\linkedlist.cpp:8:1: note:                 node::node(const node&)

Now, I am a rookie in coding and when I googled this problem, I found that a default constructor have to be constructed. I know how to create a constructor but not a member initialized list constructor.

hlp me, pls b0ss.