/***************************************************************************
* 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: Reverse each pair of nodes, such that abcdefg
* becomes badcfeg.
*****************************************************************/
public void reverseInPairs() {
for (Node t = head; null != t && null != t.next; t = t.next.next) {
swap(t, t.next);
}
}
private void swap(Node a, Node b) {
int tmp = a.data;
a.data = b.data;
b.data = tmp;
}
}
public class SinglyLinkedListTest {
/**
* Test of reverseInPairs method, of class SinglyLinkedList.
*/
@Test
public void testReverseInPairs() {
System.out.println("reverseInPairs");
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]);
}
assertTrue(Arrays.equals(input, linkedList.toArray()));
linkedList.reverseInPairs();
int[] exp = {4, 9, 2, 5, 12, 1, 7, 6, 8, 4, 0, 3, 19, 16, 11};
assertTrue(Arrays.equals(exp, linkedList.toArray()));
}
}
