[Week4](gmlwls96) Merge two sorted lists

Author: gmlwls96

merge-two-sorted-lists/gmlwls96.kt

@@ -8,7 +8,43 @@
  * }
  */
 class Solution {
+    // 시간, 공간 : o(n+m),
     fun mergeTwoLists(list1: ListNode?, list2: ListNode?): ListNode? {
-
+        var currentList1: ListNode? = list1
+        var currentList2: ListNode? = list2
+        val answerList = LinkedList<Int>()
+        while (currentList1 != null || currentList2 != null) {
+            when {
+                currentList1 == null -> {
+                    answerList.offer(currentList2!!.`val`)
+                    currentList2 = currentList2.next
+                }
+                currentList2 == null -> {
+                    answerList.offer(currentList1.`val`)
+                    currentList1 = currentList1.next
+                }
+                currentList1.`val` <= currentList2.`val` -> {
+                    answerList.offer(currentList1.`val`)
+                    currentList1 = currentList1.next
+                }
+                currentList2.`val` < currentList1.`val` -> {
+                    answerList.offer(currentList2.`val`)
+                    currentList2 = currentList2.next
+                }
+            }
+        }
+        var answer: ListNode? = null
+        var currentAnswer: ListNode? = null
+        while (answerList.isNotEmpty()) {
+            val num = answerList.poll()
+            if (answer == null) {
+                answer = ListNode(num)
+                currentAnswer = answer
+            } else {
+                currentAnswer?.next = ListNode(num)
+                currentAnswer = currentAnswer?.next
+            }
+        }
+        return answer
     }
 }