/***************************************************************************
* 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;
/****************************************************************
* Statement:
* Add the given element before the head of the list
* so that this element becomes the new head.
*
* Time Complexity of Solution:
* Best = Average = Worst = O(1).
***************************************************************/
public void addToHead(int el) {
head = new Node(el, head);
if (null == tail) {
tail = head;
}
}
}
public class SinglyLinkedListTest {
/**
* Test of addToHead method, of class SinglyLinkedList.
*/
@Test
public void testAddToHead() {
System.out.println("addToHead");
int[] input = {9, 4, 5, 2, 1, 12, 6, 7, 4, 8, 3, 0, 16, 19, 11, 17, 13};
SinglyLinkedList linkedList = new SinglyLinkedList();
for (int i = 0; i < input.length; i++) {
assertEquals(i, linkedList.size());
linkedList.addToHead(input[i]);
}
int ndx = input.length;
for (Node n = linkedList.head; null != n; n = n.next) {
assertEquals(input[--ndx], n.data);
}
assertEquals(0, ndx);
}
}
