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Question078.java
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Question078.java
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package com.hncboy.swordreferstoofferspecial;
/**
* @author hncboy
* @date 2022/1/12 9:11
* 剑指 Offer II 078.合并排序链表
*
* 给定一个链表数组,每个链表都已经按升序排列。
* 请将所有链表合并到一个升序链表中,返回合并后的链表。
*
* 示例 1:
* 输入:lists = [[1,4,5],[1,3,4],[2,6]]
* 输出:[1,1,2,3,4,4,5,6]
* 解释:链表数组如下:
* [
* 1->4->5,
* 1->3->4,
* 2->6
* ]
* 将它们合并到一个有序链表中得到。
* 1->1->2->3->4->4->5->6
*
* 示例 2:
* 输入:lists = []
* 输出:[]
*
* 示例 3:
* 输入:lists = [[]]
* 输出:[]
*
* 提示:
* k == lists.length
* 0 <= k <= 10^4
* 0 <= lists[i].length <= 500
* -10^4 <= lists[i][j] <= 10^4
* lists[i] 按 升序 排列
* lists[i].length 的总和不超过 10^4
*
* 注意:本题与主站 23 题 {@link com.hncboy.MergeKSortedLists}相同: https://leetcode-cn.com/problems/merge-k-sorted-lists/
* 通过次数 5,865 提交次数 9,122
*
* 来源:力扣(LeetCode)
* 链接:https://leetcode-cn.com/problems/vvXgSW
* 著作权归领扣网络所有。商业转载请联系官方授权,非商业转载请注明出处。
*/
public class Question078 {
public ListNode mergeKLists(ListNode[] lists) {
if (lists.length == 0) {
return null;
}
return solve(lists, 0, lists.length - 1);
}
private ListNode solve(ListNode[] lists, int left, int right) {
if (left == right) {
return lists[left];
}
int mid = (left + right) / 2;
// 合并左右两个链表
return merge(solve(lists, left, mid), solve(lists, mid + 1, right));
}
private ListNode merge(ListNode leftNode, ListNode rightNode) {
ListNode dummy = new ListNode(-1);
ListNode curr = dummy;
while (leftNode != null && rightNode != null) {
if (leftNode.val < rightNode.val) {
curr.next = leftNode;
leftNode = leftNode.next;
} else {
curr.next = rightNode;
rightNode = rightNode.next;
}
curr = curr.next;
}
curr.next = leftNode != null ? leftNode : rightNode;
return dummy.next;
}
private static class ListNode {
int val;
ListNode next;
ListNode() {
}
ListNode(int val) {
this.val = val;
}
ListNode(int val, ListNode next) {
this.val = val;
this.next = next;
}
}
}