23 Merge k Sorted List solution

typescript/23-Merge-k-Sorted-Lists.ts

@@ -0,0 +1,52 @@
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ * val: number
+ * next: ListNode | null
+ * constructor(val?: number, next?: ListNode | null) {
+ * this.val = (val===undefined ? 0 : val)
+ * this.next = (next===undefined ? null : next)
+ * }
+ * }
+ */
+
+function mergeKLists(lists: Array<ListNode | null>): ListNode | null {
+ if (lists.length === 0) return null
+
+ while (lists.length > 1) {
+ let resultList = []
+
+ for (let i = 0; i < lists.length; i += 2) {
+ let list1 = lists[i]
+ let list2
+ if (i + 1 > lists.length) list2 = null
+ else list2 = lists[i + 1]
+ resultList.push(mergeList(list1, list2))
+ }
+
+ lists = resultList
+ }
+ return lists[0] || null
+}
+
+function mergeList(
+ list1: ListNode | null,
+ list2: ListNode | null
+): ListNode | null {
+ let dummyNode: ListNode | null = new ListNode()
+ let tail = dummyNode
+
+ while (list1 && list2) {
+ if (list1.val < list2.val) {
+ tail.next = list1
+ list1 = list1.next
+ } else {
+ tail.next = list2
+ list2 = list2.next
+ }
+ tail = tail.next
+ }
+ tail.next = list1 || list2
+
+ return dummyNode.next
+}