public void setPrevious(LinkListNode p)
{
prev = p;
if (p != null && p.next != this)
{
p.setNext(this);
}
}
public LinkListNode clone()
{
LinkListNode next2 = null;
if (next != null)
{
next2 = next.clone();
}
LinkListNode head2 = new LinkListNode(data, next2, null);
return head2;
}
public LinkListNode clone()
{
LinkListNode next2 = null;
if (next != null)
{
next2 = next.clone();
}
LinkListNode head2 = new LinkListNode(data, next2, null);
return(head2);
}
public void setNext(LinkListNode n)
{
next = n;
if (this == last)
{
last = n;
}
if (n != null && n.prev != this)
{
n.setPrevious(this);
}
}
public void setNext(LinkListNode n)
{
next = n;
if (this == last)
{
last = n;
}
if (n != null && n.prev != this)
{
n.setPrevious(this);
}
}
//method 2, recursion. O(n) time, O(n) space, start with counter = 0
static LinkListNode kthToLastEleRecursive(LinkListNode head, int k, Index idx) {
if (head == null) {
return null;
}
LinkListNode node = kthToLastEleRecursive(head.next, k, idx);
idx.value += 1;
if (idx.value == k)
{
return head;
}
return node;
}
//method 2, recursion. O(n) time, O(n) space, start with counter = 0
static LinkListNode kthToLastEleRecursive(LinkListNode head, int k, Index idx)
{
if (head == null) {
return null;
}
LinkListNode node = kthToLastEleRecursive(head.next, k, idx);
idx.value += 1;
if (idx.value == k)
{
return head;
}
return node;
}
//mehtod 3, 2 pointers, iterative, O(n) time
static LinkListNode kthToLastEleTwoPointer(LinkListNode head, int k) {
LinkListNode p1 = head;
LinkListNode p2 = head;
for (int i = 0; i < k; i++) {
if (p2 == null)
return null;
p2 = p2.next;
}
while (p2 != null) {
p1 = p1.next;
p2 = p2.next;
}
return p1;
}
//mehtod 3, 2 pointers, iterative, O(n) time
static LinkListNode kthToLastEleTwoPointer(LinkListNode head, int k)
{
LinkListNode p1 = head;
LinkListNode p2 = head;
for (int i = 0; i < k; i++) {
if (p2 == null)
return null;
p2 = p2.next;
}
while (p2 != null) {
p1 = p1.next;
p2 = p2.next;
}
return p1;
}
{//return kth to last: implement an algorithm to find the kth to last elment of a single linked list.
static void Main(string[] args)
{
//need test later
LinkListNode first = new LinkListNode(0, null, null);
LinkListNode head = first;
LinkListNode second = first;
for (int i = 1; i < 7; i++)
{
second = new LinkListNode(i, null, null);
first.setNext(second);
second.setPrevious(first);
first = second;
}
for (int i = 0; i <= 7 + 1; i++)
{
//Console.WriteLine(kthToLastEleTwoPointer(head, i).data);
LinkListNode node = kthToLastEle(head, i);
String nodeValue = node == null ? "null" : "" + node.data;
Console.WriteLine(nodeValue);
}
}
//method 1, straghit forward, get length, index = length - k + 1, return element at index. O(N) time and O(1) space
static LinkListNode kthToLastEle(LinkListNode head, int k) {
LinkListNode n = head;
int length = 1;
while (n.next != null) {
n = n.next;
length++;
}
int index = length - k - 1;
length = 0 ;
n = head;
while (n != null) {
if (length == index)
return n;
n = n.next;
length++;
}
return null;
}
//method 1, straghit forward, get length, index = length - k + 1, return element at index. O(N) time and O(1) space
static LinkListNode kthToLastEle(LinkListNode head, int k)
{
LinkListNode n = head;
int length = 1;
while (n.next != null) {
n = n.next;
length++;
}
int index = length - k - 1;
length = 0 ;
n = head;
while (n != null) {
if (length == index)
return n;
n = n.next;
length++;
}
return null;
}
public LinkListNode(int d, LinkListNode n, LinkListNode p)
{
data = d;
setNext(n);
setPrevious(p);
}
//return kth to last: implement an algorithm to find the kth to last elment of a single linked list.
static void Main(string[] args)
{
//need test later
LinkListNode first = new LinkListNode(0, null, null);
LinkListNode head = first;
LinkListNode second = first;
for (int i = 1; i < 7; i++)
{
second = new LinkListNode(i, null, null);
first.setNext(second);
second.setPrevious(first);
first = second;
}
for (int i = 0; i <= 7 + 1; i++)
{
//Console.WriteLine(kthToLastEleTwoPointer(head, i).data);
LinkListNode node = kthToLastEle(head, i);
String nodeValue = node == null ? "null" : "" + node.data;
Console.WriteLine(nodeValue);
}
}
static LinkListNode kthToLastEleRecursive(LinkListNode head, int k)
{
Index idx = new Index();
return kthToLastEleRecursive(head, k, idx);
}
public LinkListNode(int d, LinkListNode n, LinkListNode p)
{
data = d;
setNext(n);
setPrevious(p);
}
static LinkListNode kthToLastEleRecursive(LinkListNode head, int k) {
Index idx = new Index();
return kthToLastEleRecursive(head, k, idx);
}
