Write the following functions for singly linked list: (1) Reverse the list (ii) Concatenate two lists.

Write the following functions for singly linked list: (1) Reverse the list (ii) Concatenate two lists.

C Program to Reverse the List

// C program to reverse a linked list
#include <stdio.h>
#include <stdlib.h>

/* Link list node */
struct Node {
	int data;
	struct Node* next;
};

/* Function to reverse the linked list */
static void reverse(struct Node** head_ref)
{
	struct Node* prev = NULL;
	struct Node* current = *head_ref;
	struct Node* next = NULL;
	while (current != NULL) {
		// Store next
		next = current->next;

		// Reverse current node's pointer
		current->next = prev;

		// Move pointers one position ahead.
		prev = current;
		current = next;
	}
	*head_ref = prev;
}

/* Function to push a node */
void push(struct Node** head_ref, int new_data)
{
	struct Node* new_node
		= (struct Node*)malloc(sizeof(struct Node));
	new_node->data = new_data;
	new_node->next = (*head_ref);
	(*head_ref) = new_node;
}

/* Function to print linked list */
void printList(struct Node* head)
{
	struct Node* temp = head;
	while (temp != NULL) {
		printf("%d ", temp->data);
		temp = temp->next;
	}
}

/* Driver code*/
int main()
{
	/* Start with the empty list */
	struct Node* head = NULL;

	push(&head, 20);
	push(&head, 4);
	push(&head, 15);
	push(&head, 85);

	printf("Given linked list\n");
	printList(head);
	reverse(&head);
	printf("\nReversed linked list \n");
	printList(head);
	getchar();
}

C Function to Concatenate the List

void concatenate(struct node *a,struct node *b)
{
    if( a != NULL && b!= NULL )
    {
        if (a->next == NULL)
            a->next = b;
        else
            concatenate(a->next,b);
    }
    else
    {
        printf("Either a or b is NULL\n");
    }
}