Merge k Sorted Lists
Updated Jan 31, 2026
Problem
You are given an array of k linked-lists lists, each linked-list is sorted in ascending order.
Merge all the linked-lists into one sorted linked-list and return it.
For this problem, linked lists are represented as arrays. Return the merged result as an array.
Constraints
k == lists.length
0 <= k <= 10^4
0 <= lists[i].length <= 500
-10^4 <= lists[i][j] <= 10^4
lists[i] is sorted in ascending order.
The sum of lists[i].length will not exceed 10^4.
Examples
Example 1
Input:
lists = [[1,4,5],[1,3,4],[2,6]]
Output:
[1,1,2,3,4,4,5,6]
Example 2
Input:
lists = []
Output:
[]
Example 3
Input:
lists = [[]]
Output:
[]
Function Signature
def mergeKLists(self, lists: list[list[int]]) -> list[int]
How to Submit
Implement a Solution class with a mergeKLists method.
Your method will be called with the input parameters and should return the answer.