Merge pull request neetcode-gh#822 from t3chkid/main

Ahmad-A0 · web-flow · commit fb15b51362e8 · 2022-08-15T17:24:28.000+01:00
Adds solution for 23.Merge k Sorted Lists in Kotlin
diff --git a/kotlin/23-Merge-k-Sorted-Lists.kt b/kotlin/23-Merge-k-Sorted-Lists.kt
@@ -0,0 +1,40 @@
+package kotlin
+
+class Solution{
+    fun mergeKLists(lists: Array<ListNode?>): ListNode? {
+        if (lists.isEmpty()) return null
+        var mergeInterval = 1
+        while (mergeInterval < lists.size) {
+            for (i in 0..lists.lastIndex step mergeInterval * 2) {
+                lists[i] = merge(lists[i], if (i + mergeInterval <= lists.lastIndex) lists[i + mergeInterval] else null)
+            }
+            mergeInterval *= 2
+        }
+        return lists[0]
+    }
+
+    private fun merge(l1: ListNode?, l2: ListNode?): ListNode? {
+        val dummyNode = ListNode(-1)
+        var currentNodeInList1 = l1
+        var currentNodeInList2 = l2
+        var currentNodeInResultantList:ListNode? = dummyNode
+
+        while(currentNodeInList1!=null && currentNodeInList2!=null){
+            if (currentNodeInList1.`val`>=currentNodeInList2.`val`){
+                currentNodeInResultantList?.next = currentNodeInList2
+                currentNodeInList2 = currentNodeInList2.next
+            }else{
+                currentNodeInResultantList?.next = currentNodeInList1
+                currentNodeInList1 = currentNodeInList1.next
+            }
+            currentNodeInResultantList = currentNodeInResultantList?.next
+        }
+
+        currentNodeInResultantList?.next = when{
+            currentNodeInList1!=null -> currentNodeInList1
+            currentNodeInList2!=null -> currentNodeInList2
+            else -> null
+        }
+        return dummyNode.next
+    }
+}
