Add merge-two-sorted-lists solution

Author: Jeehay28

merge-two-sorted-lists/Jeehay28.js

@@ -0,0 +1,34 @@
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val, next) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.next = (next===undefined ? null : next)
+ * }
+ */
+/**
+ * @param {ListNode} list1
+ * @param {ListNode} list2
+ * @return {ListNode}
+ */
+
+// Time Complexity: O(m + n)
+// Space Complexity: O(m + n)  
+
+var mergeTwoLists = function(list1, list2) {
+
+    
+    if(!(list1 && list2)) {
+        return list1 || list2;
+    }
+
+    if(list1.val < list2.val) {
+        list1.next = mergeTwoLists(list1.next, list2);
+        return list1;
+    } else {
+        list2.next = mergeTwoLists(list1, list2.next);
+        return list2;
+    }
+    
+};
+
+