Merge k Sorted Lists Solutions in Go

package leetcode

import (
	"github.com/halfrost/LeetCode-Go/structures"
)

// ListNode define
type ListNode = structures.ListNode

/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func mergeKLists(lists []*ListNode) *ListNode {
	length := len(lists)
	if length < 1 {
		return nil
	}
	if length == 1 {
		return lists[0]
	}
	num := length / 2
	left := mergeKLists(lists[:num])
	right := mergeKLists(lists[num:])
	return mergeTwoLists1(left, right)
}

func mergeTwoLists1(l1 *ListNode, l2 *ListNode) *ListNode {
	if l1 == nil {
		return l2
	}
	if l2 == nil {
		return l1
	}
	if l1.Val < l2.Val {
		l1.Next = mergeTwoLists1(l1.Next, l2)
		return l1
	}
	l2.Next = mergeTwoLists1(l1, l2.Next)
	return l2
}