refactor 21

fishercoder1534 · fishercoder1534 · commit 9b1b3efaa386 · 2020-01-17T07:02:44.000-08:00
diff --git a/src/main/java/com/fishercoder/solutions/_21.java b/src/main/java/com/fishercoder/solutions/_21.java
@@ -6,10 +6,21 @@
  * 21. Merge Two Sorted Lists
  *
  * Merge two sorted linked lists and return it as a new list.
- * The new list should be made by splicing together the nodes of the first two lists.*/
+ * The new list should be made by splicing together the nodes of the first two lists.
+ *
+ * Example:
+ * Input: 1->2->4, 1->3->4
+ * Output: 1->1->2->3->4->4
+ *
+ * */
 
 public class _21 {
     public static class Solution1 {
+        /**
+         * recursive solution
+         * Time: O(m+n)
+         * Space: O(m+n)
+         * */
         public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
             if (l1 == null) {
                 return l2;
