Grokking #204

class Solution {

  public ListNode swapNodes(ListNode head, int k) {

    ListNode n1 = null;
    ListNode n2 = null;

    ListNode first = head;
    ListNode second = head;
    for (int i = 1; i <= k; i++) {

      if (i == k) {
        n1 = second;
      }

      second = second.next;
    }

    while (second != null) {
      first = first.next;
      second = second.next;
    }

    n2 = first;

    // swap n1 and n2 values
    int tmp = n1.val;
    n1.val = n2.val;
    n2.val = tmp;

    return head;

  }
}