How to delete a node from a circular linked list in Java?

Question

Given a Circular linked list write a method in Java to delete a node.

Answer 1

There are really four cases to consider for this.

Case 1:

Is the list empty? If so return null or return

Case 2:

There is only one element in the list. Set the pointer to null and the list to null.

Case 3:

Delete something in the front of the list. In this case we have a few steps.

Steps:

1. Make a temporary pointer to the list.
2. Move to the end of the list.
3. Set the temp pointer to the front of the list.
4. Move the front of the list forward.
5. Set temp's pointer to null.
6. Set the end of the list to point to the new front of the list.

Case 4:

Delete something in this format 1->2->3-> where we are deleting the middle item. Note. This works for deleting the last item as well since it loops back around to 1.

Steps

1. Make a temp pointer to the list.
2. Move the temp pointer forward until we find the data to delete.
3. Make a delete node (Example Node delete) and set it to temp's pointer.
4. Set temp to skip over the node we are deleting.

5. Set the delete node's pointer to null.

   public void delete(int data) {
       // Null list case
       if(list == null) return;
   
       // Delete the only element case
       if(list.data == data && list.next.data == list.data) {
           list.next = null;
           list = null;
           return;
       }
   
       // Delete the front of the list case
       if(list.data == data) {
   
           // Move to the end of the list
           Node end = list;
           while(end.next.data != list.data) {
               end = end.next;
           }
   
           Node temp = list;   
           list = list.next;
           temp.next = null;
           end.next = list;
           return;
       }
   
       // Delete something in the middle
       Node temp = list;
       while(temp.next.data != data && temp.next.data != list.data) {
           temp = temp.next;
       }
   
       // We circled the list and did not find the element to delete       
       if(temp.next.data == list.data) return; 
   
       Node del = temp.next;
       temp.next = temp.next.next;
       del.next = null;
   }