Create 24 Swap Nodes in Pairs.java

Author: SharmaTushar1

java/24 Swap Nodes in Pairs.java

@@ -0,0 +1,31 @@
+//Iterative version
+class Solution {
+    public ListNode swapPairs(ListNode head) {
+        if (head == null || head.next == null) return head;
+        ListNode dummy = new ListNode(0);
+        dummy.next = head;
+        ListNode temp = dummy;
+        while (temp.next!=null && temp.next.next!=null) {
+            ListNode first = temp.next;
+            ListNode second = temp.next.next;
+            temp.next = second;
+            first.next = second.next;
+            second.next = first;
+            temp = first;
+        }
+        return dummy.next;
+        
+    }
+}
+
+//Recursive version
+class Solution {
+    public ListNode swapPairs(ListNode head) {
+        if (head == null || head.next == null) 
+            return head;
+        ListNode p = head.next;
+        head.next = swapPairs(head.next.next);
+        p.next = head;
+        return p;
+    }
+}