Update solution.ts

Author: javadev

src/main/ts/g0001_0100/s0023_merge_k_sorted_lists/solution.ts

@@ -1,8 +1,10 @@
 // #Hard #Top_100_Liked_Questions #Top_Interview_Questions #Heap_Priority_Queue #Linked_List
 // #Divide_and_Conquer #Merge_Sort #Big_O_Time_O(k*n*log(k))_Space_O(log(k))
-// #2023_08_29_Time_75_ms_(97.06%)_Space_47.3_MB_(98.42%)
+// #2023_10_09_Time_76_ms_(94.52%)_Space_47.9_MB_(84.35%)
 
-/**
+import { ListNode } from '../../com_github_leetcode/listnode'
+
+/*
  * Definition for singly-linked list.
  * class ListNode {
  *     val: number
@@ -13,51 +15,46 @@
  *     }
  * }
  */
-function mergeKLists(lists: Array<ListNode | null>): ListNode | null {
-    if (lists.length === 0) {
-        return null
+const merge2Lists = (list1: ListNode | null, list2: ListNode | null): ListNode | null => {
+    if (!list1 || !list2) {
+        return list1 || list2
     }
-    return mergeKListsRecursive(lists, 0, lists.length)
-}
-
-function mergeKListsRecursive(lists: Array<ListNode | null>, leftIndex: number, rightIndex: number): ListNode | null {
-    if (rightIndex > leftIndex + 1) {
-        const mid = Math.floor((leftIndex + rightIndex) / 2)
-        const left = mergeKListsRecursive(lists, leftIndex, mid)
-        const right = mergeKListsRecursive(lists, mid, rightIndex)
-        return mergeTwoLists(left, right)
-    } else {
-        return lists[leftIndex]
+    const tempHead = new ListNode()
+    let current = tempHead
+    let l1 = list1
+    let l2 = list2
+    while (l1 || l2) {
+        if (!l1) {
+            current.next = l2
+            break
+        }
+        if (!l2) {
+            current.next = l1
+            break
+        }
+        if (l1.val < l2.val) {
+            current.next = l1
+            l1 = l1.next
+        } else {
+            current.next = l2
+            l2 = l2.next
+        }
+        current = current.next
     }
+    return tempHead.next
 }
 
-function mergeTwoLists(left: ListNode | null, right: ListNode | null): ListNode | null {
-    if (left === null) {
-        return right
-    }
-    if (right === null) {
-        return left
-    }
-    let res: ListNode | null
-    if (left.val <= right.val) {
-        res = left
-        left = left.next
-    } else {
-        res = right
-        right = right.next
-    }
-    let node = res
-    while (left !== null || right !== null) {
-        if (right === null || left.val <= right.val) {
-            node.next = left
-            left = left.next
-        } else {
-            node.next = right
-            right = right.next
+const mergeKLists = (lists: Array<ListNode | null>): ListNode | null => {
+    while (lists.length > 1) {
+        const mergedLists = []
+        for (let i = 0; i < lists.length; i += 2) {
+            const list1 = lists[i]
+            const list2 = lists[i + 1] ?? null
+            mergedLists.push(merge2Lists(list1, list2))
         }
-        node = node.next
+        lists = mergedLists
     }
-    return res
+    return lists[0] ?? null
 }
 
 export { mergeKLists }