How to fix casting a pointer to an integer? - c

Question

I'm writing a program that creates a doubly linked list out of an array. Here's the code so far:
#include<stdio.h>
#include<stdlib.h>
struct Node {
int data;
struct Node *next;
struct Node *previous;
}
struct Node *create_dll_from_array(int array[], int x) {
int i;
struct Node *newNode, *temp, *head;
for (i=0; i<x; i++) {
newNode = (struct Node *)malloc(sizeof(struct Node));
newNode->data = *(array+i);
if (i=0) {
head = newNode;
temp = newNode;
newNode->next = NULL;
newNode->previous = NULL;
}
else {
*** temp->next = (struct Node*) newNode->data;
newNode->next = NULL;
*** newNode->previous = (struct Node*) temp->data;
temp = newNode;
}
}
return head;
}
int main(){
int array[5] = {11,2,7,22,4};
struct Node* head;
head = create_dll_from_array(array,5);
return 0;
}
So in the lines with ***, I'm getting the error: warning: cast to pointer from integer of different size
I don't know whether the program itself actually works, just asking about those two lines and why they aren't working. Thanks!

Answer 1

How to fix casting a pointer to an integer?
Don't assign an int to a pointer and then the need for casting is gone.
Assign a pointer to a pointer.
// temp->next = (struct Node*) newNode->data;
temp->next = newNode;

Answer 2

You can improve on these things:
Always initialize your pointer with NULL. This will guard you against the pointer pointing to an invalid address.
Do not hard code the array size value. Calculate it.
In the if condition you have used assignment =. Change that to equality check ==. If you will not do this, your program will crash.
just asking about those two lines and why they aren't working
It is because, temp->next points to a memory location of type struct node. You cant assign it an integer value (as you were doing). I have reproduced your full code below some of your lines commented.
#include<stdio.h>
#include<stdlib.h>
struct Node {
int data;
struct Node *next;
struct Node *previous;
};
struct Node *create_dll_from_array(int array[], int x) {
int i;
// struct Node *newNode, *temp, *head;
struct Node *newNode= NULL, *temp=NULL, *head=NULL;
for (i=0; i<x; i++) {
newNode = (struct Node *)malloc(sizeof(struct Node));
newNode->data = *(array+i);
// if (i=0) { Its wrong
if (i==0) {
head = newNode;
temp = newNode;
newNode->next = NULL;
newNode->previous = NULL;
}
else {
// temp->next = (struct Node*) newNode->data; // issue
temp->next = (struct Node*) newNode;
newNode->next = NULL;
// newNode->previous = (struct Node*) temp->data; //issue
newNode->previous = (struct Node*) temp; //issue
temp = newNode;
}
}
return head;
}
int main(){
// int array[5] = {11,2,7,22,4};
int array[] = {11,2,7,22,4};
struct Node* head;
// head = create_dll_from_array(array,5);
head = create_dll_from_array(array,sizeof(array)/sizeof(*array));
return 0;
}
Few more optimization that you can do is that inside your create_dll function, the if condition is hit only for the first time. You can move that to else condition and make your else condition your if condition