/***************************************************************************
* 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;
/*****************************************************************
* Time Complexity of Solution:
* O(n).
*
* Description: Delete all duplicates from this list, such that
* iabcdeafgdc becomes iabcdefg
*
* Technical Details: The easiest way to remove duplicates from
* a collection tends to be with a hashmap. Here is a process:
* 0] traverse the list, sending data to a linked hashmap, which
* discards duplicates. (Do deleteFromHead if acceptable)
* 1] empty the linked hashmap into a new linked list.
* Time Complexity is O(n); Space Complexity is O(n)
*****************************************************************/
public void deleteDuplicates() {//min, max, avg, sum, size
Map<Integer, Integer> noDups = new LinkedHashMap<Integer, Integer>();
Node t = null;
while (null != (t = this.deleteFromHead())) //if(!noDups.containsKey(t.data)): not necessary
{
noDups.put(t.data, 1);
}
//reconstruct linkedlist
for (int k : noDups.keySet()) {
addToTail(k);
}
}
}
public class SinglyLinkedListTest {
/**
* Test of deleteDuplicates method, of class SinglyLinkedList.
*/
@Test
public void testDeleteDuplicates() {
System.out.println("deleteDuplicates");
int[] input = {2, 19, 11, 5, 17, 11, 1, 17, 2, 11};
SinglyLinkedList linkedList = new SinglyLinkedList();
for (int i = 0; i < input.length; i++) {
linkedList.addToTail(input[i]);
}
int[] exp = {2, 19, 11, 5, 17, 1};
linkedList.deleteDuplicates();
assertTrue(Arrays.equals(exp, linkedList.toArray()));
}
}
