@@ -0,0 +1,486 @@
+/**%0A * Definition for singly-linked list.%0A * public class ListNode %7B%0A *     int val;%0A *     ListNode next;%0A *     ListNode(int x) %7B val = x; %7D%0A * %7D%0A */%0Apublic class Solution %7B%0A    public ListNode swapPairs(ListNode head) %7B%0A        if(head == null %7C%7C head.next == null)%7B%0A            return head;%0A        %7D%0A        ListNode tmp = head.next.next;%0A        ListNode newHead = head.next;%0A        newHead.next = head;%0A        newHead.next.next = swapPairs(tmp);%0A        return newHead;%0A    %7D%0A%7D

Q24 Swap Nodes in Pairs