Swap Kth node from start and end of a LinkedList

/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode() {} * ListNode(int val) { this.val = val; } * ListNode(int val, ListNode next) { this.val = val; this.next = next; } * } */ class Solution { public ListNode swapNodes(ListNode head, int k) { ListNode slow = head; ListNode fast = head; ListNode prev = null; while(k-->0){ prev = fast; fast = fast.next; } while(fast!=null){ slow = slow.next; fast = fast.next; } int temp = slow.val; slow.val = prev.val; prev.val = temp; return head; } }