FastPrepMerge K Sorted Linked Lists
Problem · Linked List

Merge K Sorted Linked Lists

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Problem statement

You are given an array lists of k singly linked lists. Every linked list is sorted in nondecreasing order.

Merge all nodes into one linked list sorted in nondecreasing order and return its head. You may relink the existing nodes.

Function

mergeKLists(lists: ListNode[]) → ListNode

Examples

Example 1

lists = [[1,4,5],[1,3,4],[2,6]]return = [1,1,2,3,4,4,5,6]

Taking the smallest current head repeatedly produces the combined sorted order.

Example 2

lists = []return = []

There are no nodes to merge.

Example 3

lists = [[],[-2,0,7],[3]]return = [-2,0,3,7]

Empty lists contribute no nodes; the remaining two lists merge in sorted order.

Constraints

  • 0 <= k <= 100
  • The total number of nodes across all lists is at most 5000.
  • -10^9 <= node.val <= 10^9
  • Every input list is sorted in nondecreasing order.

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public ListNode mergeKLists(ListNode[] lists) {
    // write your code here
}
lists[[1,4,5],[1,3,4],[2,6]]
expected[1,1,2,3,4,4,5,6]
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