reverse_linked_list_iter.c

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

typedef struct Node {
  int data;
  struct Node * next;
} Node;

Node * create_node(int val){
  Node * temp = (Node *)malloc(sizeof(Node));
  if(temp){
    temp->data = val;
    temp->next = NULL;
  }
  return temp;
}
/* This function inserts node at the head of linked list */
void push(Node **headRef, int data){
	Node * new_node  = (Node *)malloc(sizeof(Node));
	new_node->data = data;
	new_node->next = *headRef;
	*headRef  = new_node;
}

void print_list(Node * head){
	while(head){
		printf("%d->", head->data);
		head = head->next;
	}
	printf("Null");
}

Node * reverse_linked_list(Node * head){
	 /* We are not passing reference to head, as we will be returning changed
	 head pointer */
	 if(!head) return NULL;
	 
	 Node * current  = head;
	 Node * previous = NULL;
	 Node * next = NULL;
	 
	 while(current){
	 	next = current ->next;
	 	current->next = previous;
	 	previous = current;
	 	current = next;
	 }
	 
	 return previous;
}

int main(void) {
	
	Node * head = NULL;
	push(&head, 3);
	push(&head, 4);
	push(&head, 5);
	push(&head, 6);
	push(&head, 7);
	
	printf("\n Original list :");
	print_list(head);
	
    	head = reverse_linked_list(head);
    	printf("\n Reverse list :");
    	print_list(head);	
	
	return 0;
}