Deletion_in_linklist.c

//Deletion of a node in a linked list
#include<stdio.h>
#include<stdlib.h>

struct node
{
    int data;
    struct node *next;
};

void addLast(struct node **head, int val)
{
    //create a new node
    struct node *newNode = malloc(sizeof(struct node));
    newNode->data = val;
    newNode->next     = NULL;

    //if head is NULL, it is an empty list
    if(*head == NULL)
         *head = newNode;
    //Otherwise, find the last node and add the newNode
    else
    {
        struct node *lastNode = *head;

        //last node's next address will be NULL.
        while(lastNode->next != NULL)
        {
            lastNode = lastNode->next;
        }

        //add the newNode at the end of the linked list
        lastNode->next = newNode;
    }

}

void deleteNode(struct node **head, int key)
{
      //temp is used to freeing the memory
      struct node *temp;

      //key found on the head node.
      //move to head node to the next and free the head.
      if((*head)->data == key)
      {
          temp = *head;    //backup to free the memory
          *head = (*head)->next;
          free(temp);
      }
      else
      {
          struct node *current  = *head;
          while(current->next != NULL)
          {
              //if yes, we need to delete the current->next node
              if(current->next->data == key)
              {
                  temp = current->next;
                  //node will be disconnected from the linked list.
                  current->next = current->next->next;
                  free(temp);
                  break;
              }
              //Otherwise, move the current node and proceed
              else
                  current = current->next;
          }
      }
}

void printList(struct node *head)
{
    struct node *temp = head;

    //iterate the entire linked list and print the data
    while(temp != NULL)
    {
         printf("%d ->", temp->data);
         temp = temp->next;
    }
    printf("NULL\n");
}

int main()
{
     struct node *head = NULL;

     addLast(&head,10);
     addLast(&head,20);
     addLast(&head,30);
     printf("Linked List Elements:\n");
     printList(head);

     //delete first node
     deleteNode(&head,10);
     printf("Deleted 10. The New Linked List:\n");
     printList(head);

     //delete last node
     deleteNode(&head,30);
     printf("Deleted 30. The New Linked List:\n");
     printList(head);

     //delete 20
     deleteNode(&head,20);
     printf("Deleted 20. The New Linked List:\n");
     printList(head);

     return 0;
}