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23-Merge-k-Sorted-Lists.ts
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23-Merge-k-Sorted-Lists.ts
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/**
* 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;
}