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Merge K Sorted Lists

HardHeap

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.

Linked lists are represented as nested objects: { val: 1, next: { val: 4, next: { val: 5, next: null } } }

Example:

Input: lists = [[1,4,5],[1,3,4],[2,6]]
Output: [1,1,2,3,4,4,5,6]
Explanation: The three sorted lists are merged into one sorted list

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 total number of nodes does not exceed 10^4