Swap Pairs in Linked List

ListNode.java

package com.interviewbytes.linkedlists;


public class ListNode {
    int val;
    ListNode next;

    ListNode(int x) {
        val = x;
    }
}

SwapPairs.java

package com.interviewbytes.linkedlists;


public class SwapPairs {

    public ListNode swapPairs(ListNode head) {

        if (head == null || head.next == null) return head;

        ListNode next = head.next.next;

        ListNode temp = head;
        head = head.next;
        head.next = temp;

        head.next.next = swapPairs(next);

        return head;
    }
}