Delete a node in singly link list

Question

How to delete a node in a singly link list with only one pointer pointing to node to be deleted?

[Start and end pointers are not known, the available information is poin

Answer 1

You can delete a node without getting the previous node, by having it mimic the following node and deleting that one instead:

void delete(Node *n) {
  if (!is_sentinel(n->next)) {
    n->content = n->next->content;
    Node *next = n->next;
    n->next = n->next->next;
    free(next);
  } else {
    n->content = NULL;
    free(n->next);
    n->next = NULL;
  }
}

As you can see, you will need to deal specially for the last element. I'm using a special node as a sentinel node to mark the ending which has content and next be NULL.

UPDATE: the lines Node *next = n->next; n->next = n->next->next basically shuffles the node content, and frees the node: Image that you get a reference to node B to be deleted in:

   A           / To be deleted
  next   --->  B
              next  --->    C
                           next ---> *sentinel*

The first step is n->content = n->next->content: copy the content of the following node to the node to be "deleted":

   A           / To be deleted
  next   --->  C
              next  --->    C
                           next ---> *sentinel*

Then, modify the next points:

   A           / To be deleted
  next   --->  C       /----------------
              next  ---|    C          |
                           next ---> *sentinel*

The actually free the following element, getting to the final case:

   A           / To be deleted
  next   --->  C
              next  --->    *sentinel*