题解 | #合并k个已排序的链表（java）#

两条和n条的合并并没有什么太大的差距

import java.util.*;
/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {

    ListNode res = null;

    public ListNode mergeKLists(ArrayList<ListNode> lists) {

        if (lists.size() == 0) {
            return res;
        }

        res = lists.get(0);

        for (int i = 1; i < lists.size(); i++) {
            merge(res, lists.get(i));
        }

        return res;
    }

    private void merge(ListNode a, ListNode b) {

        ListNode head = new ListNode(-1);
        ListNode cur = head;

        while (a != null && b != null) {
            if (a.val < b.val) {
                cur.next = a;
                a = a.next;
                cur = cur.next;
            } else {
                cur.next = b;
                b = b.next;
                cur = cur.next;
            }
        }

        while (a != null) {
                cur.next = a;
                a = a.next;
                cur = cur.next;
        }

        while (b != null) {
                cur.next = b;
                b = b.next;
                cur = cur.next;
        }

        res = head.next;
    }
}