LeetCode Remove nth element from the end from linked list in Swift.

RemoveNTh.swift

class ListNode{
    var val:Int?
    var next:ListNode?
    init(){}
    
    init(x:Int){
        self.val = x
    }
}


func createLinkedList()->ListNode {
    var l1 = ListNode(x:1)
    var l2 = ListNode(x:2)
    var l3 = ListNode(x:3)
    var l4 = ListNode(x:4)
    var l5 = ListNode(x:5)
    
//    l1.next = l2
//    l2.next = l3
//    l3.next = l4
//    l4.next = l5
    return l1
}




func removeNTH(head:ListNode, n:Int)->ListNode?{
    var firstNode:ListNode! = head
    var secondNode:ListNode! = head

    //increment the first node to N position from the beginning
    for var i = 0; i < n+1; i++ {
      firstNode = firstNode.next
    }
    
    //checking for boundary problem
    if firstNode == nil {
        return head.next
    }
    
    //now continune node by node checking if we didn't reach the end
    while firstNode != nil{
        firstNode = firstNode.next
        secondNode = secondNode.next
    }
    secondNode.next = secondNode.next?.next
    return head
}



func printKeys(list:ListNode){
    var i = 0
    var current:ListNode! = list
    while ( current != nil)
    {
        i++;
        println(current.val)
        current = current.next
      
        if (i > 10) { break }
    }
}
var node = removeNTH(createLinkedList(), 1)
printKeys(node!)