【LeetCode】#23合并K个排序链表(Merge k Sorted Lists)

【LeetCode】#23合并K个排序链表(Merge k Sorted Lists)

题目描述

合并 k 个排序链表，返回合并后的排序链表。

示例

输入:
[
1->4->5,
1->3->4,
2->6
]
输出: 1->1->2->3->4->4->5->6

Description

Merge k sorted linked lists and return it as one sorted list.

Example

Input:
[
1->4->5,
1->3->4,
2->6
]
Output: 1->1->2->3->4->4->5->6

解法

class Solution {
    public ListNode mergeKLists(ListNode[] lists) {
        
        if(lists.length==0){
            return null;
        }
        
        int sum = 0;
        for(int i=0; i<lists.length; i++){
            ListNode l = lists[i];
            while(l!=null){
                sum++;
                l = l.next;
            }
        }
        int[] nums = new int[sum];
        int k = 0;
        for(int i=0; i<lists.length; i++){
            ListNode l = lists[i];
            while(l!=null){
                nums[k++] = l.val;
                l = l.next;
            }
        }
        
        if(nums.length==0){
            return null;
        }
        
        Arrays.sort(nums);
        ListNode head = new ListNode(nums[0]);
        ListNode l = head;
        for(int i=1; i<nums.length; i++){
            head.next = new ListNode(nums[i]);
            head = head.next;
        }
        return l;
        
    }
}