LeetCode – Refresh – Sort List

Use merge sort. Recursively call the function:

 1 /**
 2  * Definition for singly-linked list.
 3  * struct ListNode {
 4  *     int val;
 5  *     ListNode *next;
 6  *     ListNode(int x) : val(x), next(NULL) {}
 7  * };
 8  */
 9 class Solution {
10 public:
11     ListNode *sortList(ListNode *head) {
12         if (!head || !head->next) return head;
13         ListNode *slow = head, *fast = head;
14         while (fast->next && fast->next->next) {
15             slow = slow->next;
16             fast = fast->next->next;
17         }
18         fast = slow->next;
19         slow->next = NULL;
20         slow = sortList(head);
21         fast = sortList(fast);
22         ListNode *result = new ListNode(0);
23         ListNode *runner = result;
24         while (slow || fast) {
25             int tmp1 = INT_MAX, tmp2 = INT_MAX;
26             if (slow) {
27                 tmp1 = slow->val;
28             }
29             if (fast) {
30                 tmp2 = fast->val;
31             }
32             if (tmp1 < tmp2) {
33                 runner->next = slow;
34                 slow = slow->next;
35             } else {
36                 runner->next = fast;
37                 fast = fast->next;
38             }
39             runner = runner->next;
40         }
41         return result->next;
42     }
43 };

posted on 2015-03-24 14:24 keepshuatishuati 阅读(133) 评论(0) 收藏举报