segmenation fault error in my linkedList -C - c

Question

I put together a few pieces of code to make a linked list that adds to head(Has a special function) and in the middle(also special function).
my problem is, i need to provide the program with numbers and insert them as nodes in my LINKEDLIST. However, my display function(to display the tree of nodes) gives back segmentation fault and so does just taking values in without any display function.
I'm fairly new to malloc so i suspect the problem is there?
Thanks
#include<stdio.h>
#include<stdlib.h>
/*LINKEDLIST STRUCT*/
struct node {
int data;
struct node *next;
};
/*Inserting head-Node*/
struct node *insert_head(struct node *head, int number)
{
struct node *temp;
temp = malloc(sizeof(struct node));
if(temp == NULL)
{
printf("Not enough memory\n");
exit(1);
}
temp->data = number;
temp->next = head;
head = temp;
return head;
}
/*Inserting inside a list*/
void after_me(struct node *me, int number)
{
struct node *temp;
temp = malloc(sizeof(struct node));
if(temp == NULL)
{
printf("Not enough memory\n");
exit(1);
}
temp->data = number;
temp->next = me->next;
me->next = temp;
}
/*PRINTING LIST*/
void display(struct node *head)
{
struct node *moving_ptr = head;
while(moving_ptr != NULL)
{
printf("%d-->",moving_ptr->data);
moving_ptr = moving_ptr->next;
}
}
int main()
{
int index;
struct node *head;
struct node *previous_node;
scanf("%d", &index);
while(index > 0)
{
/*allocating in List */
if(head == NULL)
head = insert_head(head,index);
else
if((head != NULL) && (index <= (head->data)))
{
struct node *temp;
head->next = temp;
temp->next = head;/*TRY INSERT HEAD FUNC.*/
}
else
if((head != NULL) && (index > (head->data)))
{
previous_node->data = index-1;
after_me(previous_node,index);
}
scanf("%d", &index);
}
display(head);
}

Answer 1

I suggest as follows.
#include <stdio.h>
#include <stdlib.h>
struct node {
int data;
struct node *next;
};
//aggregated into one place
struct node *new_node(int number){
struct node *temp;
if(NULL == (temp = malloc(sizeof(*temp)))){
printf("\nNot enough memory\n");
exit(1);
}
temp->data = number;
temp->next = NULL;
return temp;
}
struct node *insert_head(struct node *head, int number) {
struct node *temp = new_node(number);
temp->next = head;
return temp;
}
void after_me(struct node *me, int number){
struct node *temp = new_node(number);
temp->next = me->next;
me->next = temp;
}
void display(struct node *head){
struct node *moving_ptr = head;
while(moving_ptr != NULL){
printf("%d", moving_ptr->data);
if(moving_ptr = moving_ptr->next)
printf("-->");
}
putchar('\n');
}
struct node *insert(struct node *me, int number){
if(me){
if(number <= me->data){
me = insert_head(me, number);
} else {
me->next = insert(me->next, number);
}
} else {
me = new_node(number);
}
return me;
}
void release(struct node *list){//Of course, you will be able to replace a simple loop(e.g while-loop).
if(list){
release(list->next);
free(list);
}
}
int main(void){
struct node *head = NULL;
int index;
while(1==scanf("%d", &index) && index > 0){
head = insert(head, index);
}
display(head);
release(head);
return 0;
}