public static ListNode SwapNodes(ListNode head, int k)
{
int count = 1;
ListNode first = head, second = head.next;
while (count < k)
{
second = second.next;
count++;
}
ListNode temp = second;
while (second.next != null)
{
first = first.next;
second = second.next;
}
int t = temp.val;
temp.val = first.val;
first.val = t;
return(head);
}
public ListNode(int val = 0, ListNode next = null)
{
this.val = val;
this.next = next;
}