public LinkedListNode FindStartOfCycle(LinkedListNode head)
{
LinkedListNode fast = head;
LinkedListNode slow = head;
while (fast!=null && slow!=null && fast.Next!=null) {
slow = slow.Next;
fast = fast.Next.Next;
if (slow==fast) {
int cycleLen = 0;
do {
cycleLen++;
slow = slow.Next;
} while (fast!=slow);
slow = head;
fast = head;
for (int i = 0; i < cycleLen; i++) {
fast = fast.Next;
}
while (slow!=fast) {
slow = slow.Next;
fast = fast.Next;
}
return slow;
}
}
return null;
}
private LinkedListNode Add(LinkedListNode l1, LinkedListNode l2, int carry)
{
if (l1 == null && l2 == null)
{
return null;
}
int value = carry;
if (l1 != null)
{
value += l1.Value;
}
if (l2 != null)
{
value += l2.Value;
}
var more = Add(l1 == null ? null : l1.Next,
l2 == null ? null : l2.Next,
value > 9 ? 1 : 0);
var result = new LinkedListNode(value % 10);
result.Next = more;
return result;
}
public LinkedListNode FindStartingNodeOfOverlappingPart(LinkedListNode h1, LinkedListNode h2)
{
// Get the length for both lists
int len1 = LinkedListNode.GetLength(h1);
int len2 = LinkedListNode.GetLength(h2);
// Advance the longer list
LinkedListNode longList;
LinkedListNode shortList;
if (len1 > len2) {
longList = h1;
shortList = h2;
} else {
longList = h2;
shortList = h1;
}
for (int i = 0; i < Math.Abs(len1-len2); i++) {
longList = longList.Next;
}
// Advance both lists and compare node
while (longList!=null && shortList!=null && longList!=shortList) {
longList = longList.Next;
shortList = shortList.Next;
}
return longList;
}
public LinkedListNode ReverseLinkedListInPairs(LinkedListNode head)
{
if (head == null)
{
return null;
}
var first = head;
var second = first.Next;
if (first == null || second == null)
{
return head;
}
while (first != null && second != null)
{
var temp = first.Next.Next;
second.Next = first;
first.Next = temp;
first = temp;
if (first != null)
{
second = first.Next;
}
}
return head.Next;
}
public LinkedListNode FindTheNthToLastElement(LinkedListNode head, int n)
{
if (head == null || n < 1)
{
return null;
}
var front = head;
var back = head;
for (int i = 0; i < n; i++)
{
if (front == null)
{
return null;
}
front = front.Next;
}
while (front.Next != null)
{
front = front.Next;
back = back.Next;
}
return back;
}
public LinkedListNode Merge(LinkedListNode a, LinkedListNode b)
{
var head = new LinkedListNode(100);
var current = head;
while (a != null && b != null) {
if (a.Value < b.Value) {
current.Next = a;
a = a.Next;
} else {
current.Next = b;
b = b.Next;
}
current = current.Next;
}
if (a != null) {
current.Next = a;
}
if (b != null) {
current.Next = b;
}
return head.Next;
}
public void BuildLinkedList()
{
node = new LinkedListNode(17);
node.Next = new LinkedListNode(2);
node.Next.Next = new LinkedListNode(2);
node.Next.Next.Next = new LinkedListNode(3);
node.Next.Next.Next.Next = new LinkedListNode(6);
node.Next.Next.Next.Next.Next = node;
}
public void It_should_return_null_if_there_is_no_cycle()
{
var head = new LinkedListNode(2);
head.Next = new LinkedListNode(5);
head.Next.Next = new LinkedListNode(7);
head.Next.Next.Next = new LinkedListNode(3);
head.Next.Next.Next.Next = new LinkedListNode(11);
Obj.FindStartOfCycle(head).Should().BeNull();
}
public void Build_linked_lists()
{
h1 = new LinkedListNode(3);
h1.Next = new LinkedListNode(1);
h1.Next.Next = new LinkedListNode(5);
h2 = new LinkedListNode(5);
h2.Next = new LinkedListNode(9);
h2.Next.Next = new LinkedListNode(2);
}
public void Build_linked_list()
{
head = new LinkedListNode(2);
head.Next = new LinkedListNode(3);
head.Next.Next = new LinkedListNode(5);
head.Next.Next.Next = new LinkedListNode(7);
head.Next.Next.Next.Next = new LinkedListNode(3);
head.Next.Next.Next.Next.Next = new LinkedListNode(11);
head.Next.Next.Next.Next.Next.Next = new LinkedListNode(3);
head.Next.Next.Next.Next.Next.Next.Next = new LinkedListNode(5);
}
public void Build_linked_lists()
{
h1 = new LinkedListNode(6);
h1.Next = new LinkedListNode(17);
h1.Next.Next = new LinkedListNode(2);
h1.Next.Next.Next = new LinkedListNode(2);
h1.Next.Next.Next.Next = new LinkedListNode(3);
h2 = new LinkedListNode(2);
h2.Next = new LinkedListNode(3);
h2.Next.Next = new LinkedListNode(5);
h2.Next.Next.Next = new LinkedListNode(4);
h2.Next.Next.Next.Next = new LinkedListNode(2);
h2.Next.Next.Next.Next.Next = h1.Next.Next;
}
public void It_should_return_start_of_the_cycle_if_there_is_a_cycle()
{
var head = new LinkedListNode(2);
head.Next = new LinkedListNode(5);
head.Next.Next = new LinkedListNode(7);
head.Next.Next.Next = new LinkedListNode(3);
head.Next.Next.Next.Next = new LinkedListNode(11);
head.Next.Next.Next.Next.Next = new LinkedListNode(6);
head.Next.Next.Next.Next.Next.Next = new LinkedListNode(7);
head.Next.Next.Next.Next.Next.Next.Next = new LinkedListNode(2);
head.Next.Next.Next.Next.Next.Next.Next.Next = new LinkedListNode(2);
head.Next.Next.Next.Next.Next.Next.Next.Next.Next = new LinkedListNode(3);
head.Next.Next.Next.Next.Next.Next.Next.Next.Next.Next = head.Next.Next.Next.Next.Next;
Obj.FindStartOfCycle(head).Should().Be(head.Next.Next.Next.Next.Next);
}
public LinkedListNode RemoveDuplicate(LinkedListNode head)
{
LinkedListNode curr = head;
LinkedListNode pre = null;
var buffer = new Dictionary<int, bool>();
while (curr != null) {
if (buffer.ContainsKey(curr.Value)) {
pre.Next = curr.Next;
} else {
buffer.Add(curr.Value, true);
pre = curr;
}
curr = curr.Next;
}
return head;
}
public void It_should_reverse_linked_list_iteratively()
{
Obj.ReverseLinkedListIterative(ref head);
head.Value.Should().Be(5);
head.Next.Value.Should().Be(3);
head.Next.Next.Value.Should().Be(11);
head.Next.Next.Next.Value.Should().Be(3);
head.Next.Next.Next.Next.Value.Should().Be(7);
head.Next.Next.Next.Next.Next.Value.Should().Be(5);
head.Next.Next.Next.Next.Next.Next.Value.Should().Be(3);
head.Next.Next.Next.Next.Next.Next.Next.Value.Should().Be(2);
head = new LinkedListNode(10);
Obj.ReverseLinkedListIterative(ref head);
head.Value.Should().Be(10);
head.Next.Should().BeNull();
head = null;
Obj.ReverseLinkedListIterative(ref head);
head.Should().BeNull();
}
public double GetMedian(LinkedListNode node)
{
LinkedListNode curr = node;
LinkedListNode start = node;
int count = 0;
// get total number of nodes and the node with minimum value
do {
count++;
curr = curr.Next;
if (start.Value <= node.Value) {
start = curr;
}
} while (curr != node);
start = start.Next;
// go to the middle of the list
for (int i = 0; i < (count - 1) / 2; i++) {
start = start.Next;
}
return count % 2 == 1 ? start.Value : (start.Value + start.Next.Value) / 2.0;
}
public LinkedListNode Add(LinkedListNode l1, LinkedListNode l2)
{
return Add(l1, l2, 0);
}
public void ReverseLinkedListIterative(ref LinkedListNode head)
{
if (head == null) {
return;
}
LinkedListNode pre = null;
LinkedListNode curr = head;
while (curr != null) {
LinkedListNode next = curr.Next;
curr.Next = pre;
pre = curr;
curr = next;
}
head = pre;
}
public void ReverseLinkedListRecursive(ref LinkedListNode head)
{
if (head == null) {
return;
}
var rest = head.Next;
if (rest == null) {
return;
}
ReverseLinkedListRecursive(ref rest);
head.Next.Next = head;
head.Next = null;
head = rest;
}
