Similar to [k-th element to last of a LinkedList]({% post_url 2016-09-07-cci-2-2 %})
Given a linked list, remove the nth node from the end of list and return its head.
For example,
Given linked list:
1->2->3->4->5
and
n = 2
After removing the second node from the end, the linked list becomes
1->2->3->5
Note: Given n will always be valid. Try to do this in one pass.
trait Node {
def value: Int
def next: Node
}
object Empty extends Node {
def value: Int = throw new Error("access empty variable")
def next: Node = throw new Error("access empty variable")
}
class NonEmpty(var value: Int, var next: Node = Empty) extends Node
def toLinkedList(lst: List[Int]): Node = {
if (lst.isEmpty) Empty
else new NonEmpty(lst.head, toLinkedList(lst.tail))
}
def printLinkedList(head: Node): Unit = head match {
case Empty =>
case node: NonEmpty => {
println(node.value)
printLinkedList(node.next)
}
}
/**
* @param head
* @param k
* @return
*/
def removeNthElement(head: Node, k: Int):Node = head match {
case Empty => head
case node: NonEmpty =>
if (node.next == Empty) Empty
else {
var prev: Node = Empty
var slow: Node = head
var fast: Node = head.next
for (i <- 0 until k - 1 if fast != Empty) {
fast = fast.next
}
while (fast != Empty) {
prev = slow
slow = slow.next
fast = fast.next
}
prev match {
case Empty => slow.next
case p:NonEmpty => {
if (p.next != Empty)
p.next = p.next.next
head
}
}
}
}
val node = removeNthElement(toLinkedList(List(1,2,3)), 2)
printLinkedList(node)
