题目

在 O(n log n) 时间复杂度和常数级空间复杂度下，对链表进行排序。

示例 1:

输入: 4->2->1->3
输出: 1->2->3->4

示例 2:

输入: -1->5->3->4->0
输出: -1->0->3->4->5

代码实现

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     public int val;
 *     public ListNode next;
 *     public ListNode(int x) { val = x; }
 * }
 */
public class Solution 
{
    public ListNode SortList(ListNode head) 
    {
        return MergeList(head);
    }
    
    ListNode MergeList(ListNode head)
    {
        if(head == null || head.next == null) 
            return head;
        ListNode slow = head, fast = head, pre = head;
        while(fast != null && fast.next != null)
        {
            pre = slow;
            slow = slow.next;
            fast = fast.next.next;
        }
        pre.next = null;
        ListNode left = MergeList(head);
        ListNode right = MergeList(slow);
        return Merge(left, right);
    }
    
    ListNode Merge(ListNode left, ListNode right)
    {
        if(left == null) 
            return right;
        if(right == null) 
            return left;
        if(left.val <= right.val)
        {
            left.next=Merge(left.next, right);
            return left;
        }
        else
        {
            right.next=Merge(left, right.next);
            return right;
        }
    }
}

实验结果

执行结果：通过
执行用时 :136 ms, 在所有 C# 提交中击败了87.32%的用户
内存消耗 :29.3 MB, 在所有 C# 提交中击败了6.25%的用户