Merge pull request neetcode-gh#67 from vrindavan/main

21-Merge-Two-Sorted-Lists Recursion alernative solution

Author: neetcode-gh

java/21-Merge-Two-Sorted-Lists.java

@@ -27,4 +27,35 @@ public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
         prev.next = list1 != null ? list1 : list2;
         return root.next;
     }
-}
+}
+
+// Solution using Recursion
+/**
+ * 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 mergeTwoLists(ListNode list1, ListNode list2) {
+        ListNode head = new ListNode(0);
+
+        if(list1 == null && list2 == null) return null;
+        if(list1 == null) return list2;
+        if(list2 == null) return list1;
+
+        if(list1.val > list2.val) {
+            head = list2;
+            list2 = list2.next;
+        } else {
+            head = list1;
+            list1 = list1.next;
+        }
+        head.next = mergeTwoLists(list1, list2);
+        return head;
+    }
+}