private Node reverse(Node current, Node tail) {
if (current == tail) {
return current;
}
Node next = reverse(current.next(), tail);
next.setNext(current);
return current;
}
public Node reverse(Node head, int k) {
// after reverse, the return node is
// the last node in the first K nodes in the original list
// which is also the head node in the reversed list
Node returnNode = null;
// for the ith K sub list, the two "previous" pointers
// would point to the (i-1)th K sub list's head and tail "after" reverse
// This means, after reversing 3,2,1, previousTail points to 3 and previousHead points 1
Node previousTail = null;
while (head != null) { // not reached the end of the list
Node tail = head;
for (int i = 1; i < k & tail.next() != null; i++) {
tail = tail.next();
}
Node nextHead = tail.next();
reverse(head, tail);
if (previousTail == null) {
// first K sub list
previousTail = head;
returnNode = tail;
} else previousTail.setNext(tail);
head.setNext(nextHead);
head = nextHead;
}
return returnNode;
}
public static void main(String[] args) {
String[] data = new String[] {"1", "2", "3", "4", "5", "6"};
Node head = new Node(data[0], null);
Node current = head;
for (int i = 1; i < data.length; i++) {
Node tmp = new Node(data[i], null);
current.setNext(tmp);
current = tmp;
}
C3_5_ReverseLinkedList runner = new C3_5_ReverseLinkedList();
int k = 3;
head = runner.reverse(head, k);
while (head != null) {
System.out.println(head.getValue() + " ");
head = head.next();
}
}