refactor: 💡 import helper function from leetcode 21

Author: dandedotdev

src/0001-1000/23/mergeKLists.ts

@@ -1,35 +1,10 @@
 import { ListNode } from 'classes/SinglyLinkedListNode'
+import { mergeTwoLists } from '0001-1000/21/mergeTwoLists2'
 
 // <Recursion, DivideAndConquer>
 // Time: O(knlogk), k is the number of lists
 // Space: O(logk)
 
-function mergeTwoLists(l1: ListNode | null, l2: ListNode | null): ListNode | null {
-    if (!l1 || !l2) {
-        return l1 ?? l2
-    }
-
-    const dummyHead = new ListNode(-1)
-    let tail = dummyHead
-    let [ptr1, ptr2]: Array<ListNode | null> = [l1, l2]
-
-    while (ptr1 && ptr2) {
-        if (ptr1.val < ptr2.val) {
-            tail.next = ptr1
-            ptr1 = ptr1.next
-        } else {
-            tail.next = ptr2
-            ptr2 = ptr2.next
-        }
-
-        tail = tail.next
-    }
-
-    tail.next = ptr1 ?? ptr2
-
-    return dummyHead.next
-}
-
 // 1. divide and conquer
 function merge(lists: Array<ListNode | null>, left: number, right: number): ListNode | null {
     if (left > right) {