Refactored Swap Nodes in Pairs.java

Author: varunu28

Medium/Swap Nodes in Pair.java

@@ -0,0 +1,30 @@
+/**
+ * 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 swapPairs(ListNode head) {
+    ListNode curr = head;
+    ListNode prev = null;
+    while (curr != null && curr.next != null) {
+      ListNode nextNode = curr.next;
+      if (curr == head) {
+        head = nextNode;
+      }
+      curr.next = nextNode.next;
+      nextNode.next = curr;
+      if (prev != null) {
+        prev.next = nextNode;
+      }
+      prev = curr;
+      curr = curr.next;
+    }
+    return head;
+  }
+}