23. Merge k Sorted Lists

Problem

https://leetcode-cn.com/problems/merge-k-sorted-lists/

Solutions

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode mergeKLists(ListNode[] lists) {
        
        if(lists.length ==  0) {
            return null;
        }
        // if(lists.length == 1) {
        //     return lists[0];
        // }
        for(int i = 1; i < lists.length; i++) {
            lists[i] = merge2Lists(lists[i-1], lists[i]);
        }
        return lists[lists.length - 1];
    }
    public ListNode merge2Lists(ListNode l1, ListNode l2) {
        ListNode newList = new ListNode();
        ListNode curr = newList;
        while(l1 != null && l2 != null) {
            if(l1.val < l2.val) {
                curr.next = l1;
                l1 = l1.next;
            } else {
                curr.next = l2;
                l2 = l2.next;
            }
            curr = curr.next;
        }
        if(l1 == null) {
            curr.next = l2;
        }
        if(l2 == null) {
            curr.next = l1;
        }
        return newList.next;
    }
}

暴力解决

1. 解决合并2个顺序链表
2. 循环调用直到合并完成整个list的有序链表

Reference