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  • 148. Sort List

    Sort a linked list in O(n log n) time using constant space complexity.

    含义:为一个列表排序,要求空间复杂度为常量

    思路:使用归并排序

     1 class Solution {
     2  private ListNode mergeNode(ListNode l1, ListNode l2) {
     3         ListNode head = new ListNode(0);
     4         ListNode p = head;
     5         while (l1 != null && l2 != null) {
     6             if (l1.val < l2.val) {
     7                 p.next = l1;
     8                 l1 = l1.next;
     9             } else {
    10                 p.next = l2;
    11                 l2 = l2.next;
    12             }
    13             p = p.next;
    14         }
    15         if (l1 != null) p.next = l1;
    16         if (l2 != null) p.next = l2;
    17         return head.next;
    18     }
    19     
    20     public ListNode sortList(ListNode head) {
    21         if (head == null || head.next == null) return head;
    22         ListNode walker = head, runner = head;
    23         while (runner != null && runner.next != null) {
    24             walker = walker.next;
    25             runner = runner.next.next;
    26         }
    27         ListNode l1 = sortList(head);
    28         ListNode l2 = sortList(walker);
    29         return mergeNode(l1, l2);        
    30     }
    31 }
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  • 原文地址:https://www.cnblogs.com/wzj4858/p/7729381.html
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