package algorithms.study;

/**

* Reverse a LinkedList

*

* created by cenkc on 5/10/2021

*/

public class ReverseLinkedList {

private static ListNode head;

public static void main(String[] args) {

ReverseLinkedList rll = new ReverseLinkedList();

rll.generateLinkedList();

rll.printLinkedList(head);

ListNode reversedLinkedList = rll.reverseLinkedList();

rll.printLinkedList(reversedLinkedList);

}

private ListNode reverseLinkedList() {

ListNode current = head;

ListNode previous = null;

while (current != null /*&& current.next != null*/) {

ListNode next = current.next;

current.next = previous;

previous = current;

current = next;

}

return previous;

}

private void generateLinkedList() {

for (int i = 0; i < 10; i++) {

addToLast(new ListNode(i));

}

}

private void addToLast(ListNode node) {

if (head == null) {

head = node;

} else {

ListNode temp = head;

while (temp.next != null) {

temp = temp.next;

}

temp.next = node;

}

}

private void printLinkedList(ListNode head) {

ListNode temp = head;

while (temp != null) {

System.out.println("val = " + temp.value);

temp = temp.next;

}

}

/*

private class ListNode {

private int value;

private ListNode next;

public ListNode(int value) {

this.value = value;

}

}

*/

}