Add scala solution for 21-Merge-Two-Sorted-Lists

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

@@ -0,0 +1,34 @@
+/**
+ * Definition for singly-linked list.
+ * class ListNode(_x: Int = 0, _next: ListNode = null) {
+ * var next: ListNode = _next
+ * var x: Int = _x
+ * }
+ */
+object Solution {
+ def mergeTwoLists(list1: ListNode, list2: ListNode): ListNode = {
+ val head = new ListNode()
+ var tail = head
+ var (ptr1, ptr2) = (list1, list2)
+
+ while (ptr1 != null && ptr2 != null) {
+ if (ptr1.x <= ptr2.x) {
+ tail.next = ptr1
+ ptr1 = ptr1.next
+ } else {
+ tail.next = ptr2
+ ptr2 = ptr2.next
+ }
+
+ tail = tail.next
+ }
+
+ if (ptr1 != null) {
+ tail.next = ptr1
+ } else if (ptr2 != null) {
+ tail.next = ptr2
+ }
+
+ return head.next
+ }
+}