/***************************************************************************
* Author: Isai Damier
* Title: Singly Linked List
* Project: geekviewpoint
* Package: datastructure
*
* Description: A LinkedList is a data structure that allows access
* to a collection of data using pointers/references. While an
* array can also be defined as above, LinkedLists and arrays differ
* in how they are stored in memory and in the operations they
* allow. Unlike an array that must be stored in a block of memory,
* the nodes of a LinkedList can be stored anywhere because each
* node has a reference to the node that succeeds it. Because the
* nodes are stored so loosely, inserting nodes into a LinkedList
* is easy; whereas in an array, all the succeeding elements must
* be shifted. Of course, insertion also means changing the size of
* the array, which means creating the entire array anew.
*
* Perhaps the greatest beauty of LinkedList is that it allows
* accessing an entire sequence of nodes using only one variable:
* a reference to the first node in the sequence.
*
* Countless operations can be performed on LinkedLists. Following
* are a few, ranging from the common to the very interesting.
**************************************************************************/
public class SinglyLinkedList {
Node head = null;
Node tail = null;
/*****************************************************************
* Description: Delete and retrieve the specified element.
*
* One of the drawbacks of LinkedList is that
* it allows no random access. Therefore deleting a random
* element is a O(n) process because the list must first be
* traversed to find the node containing the element.
*
* Technical Details:
* 0] If el is the head, simply delete from head and return: O(1).
* 1] If el is the tail, simply delete from tail and return: O(1).
* 2] Otherwise, find the node containing el, and its parent.
* 3] If said node is not null, give its parent custody of its child.
* 4] Return the node.
*****************************************************************/
public Node delete(int el) {
if (el == head.data)//O(1)
{
return this.deleteFromHead();
}
if (el == tail.data)//O(1)
{
return this.deleteFromTail();
}
Node del = null;
Node parent = null, curr = head;
while (null != curr && el != curr.data) {
parent = curr;
curr = curr.next;
}
if (null != curr) {
parent.next = curr.next;
}
return curr;
}
}
public class SinglyLinkedListTest {
/**
* Test of delete method, of class SinglyLinkedList.
*/
@Test
public void testDelete_int() {
System.out.println("delete");
int[] input = {9, 4, 5, 2, 1, 12, 6, 7, 4, 8, 3, 0, 16, 19, 11};
SinglyLinkedList linkedList = new SinglyLinkedList();
for (int i = 0; i < input.length; i++) {
linkedList.addToTail(input[i]);
}
assertEquals(input[0], linkedList.delete(input[0]).data);
assertEquals(input[5], linkedList.delete(input[5]).data);
int last = input.length - 1;
assertEquals(input[last], linkedList.delete(input[last]).data);
int[] expected = {4, 5, 2, 1, 6, 7, 4, 8, 3, 0, 16, 19};
assertEquals(null, linkedList.delete(51));
assertTrue(Arrays.equals(expected, linkedList.toArray()));
}
}
