Swapping_Nodes_in_a_Linked_List.java

public class Swapping_Nodes_in_a_Linked_List {
  public static void main(String[] args) {
  }

  public ListNode swapNodes(ListNode head, int k) {
    ListNode curr = head;
    int len = 0;
    while (curr != null) {
      len++;
      curr = curr.next;
    }
    int fromStart = k, fromEnd = len - k;
    curr = head;
    while (fromStart > 1) {
      curr = curr.next;
      fromStart--;
    }
    ListNode node1 = curr;
    curr = head;
    while (fromEnd > 0) {
      curr = curr.next;
      fromEnd--;
    }
    int temp = node1.val;
    node1.val = curr.val;
    curr.val = temp;

    return head;
  }
}