LeetCode: Sort List

merge sort

 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 *mergesort(ListNode *p, ListNode *q) {
12         ListNode *head = NULL;
13         ListNode *cur = NULL;
14         while (p && q) {
15             if (p->val < q->val) {
16                 if (!head) head = cur = p;
17                 else {
18                     cur->next = p;
19                     cur = cur->next;
20                 }
21                 p = p->next;
22             }
23             else {
24                 if (!head) head = cur = q;
25                 else {
26                     cur->next = q;
27                     cur = cur->next;
28                 }
29                 q = q->next;
30             }
31         }
32         if (p) cur->next = p;
33         else cur->next = q;
34         return head;
35     }
36     ListNode *sortList(ListNode *head) {
37         if (!head || !head->next) return head;
38         ListNode *p, *q;
39         p = q = head;
40         while (q && q->next) {
41             q = q->next->next;
42             if (!q) break;
43             p = p->next;
44         }
45         q = p->next;
46         p->next = NULL;
47         p = sortList(head);
48         q = sortList(q);
49         return mergesort(p, q);
50     }
51 };

 1 /**
 2  * Definition for singly-linked list.
 3  * public class ListNode {
 4  *     public int val;
 5  *     public ListNode next;
 6  *     public ListNode(int x) { val = x; }
 7  * }
 8  */
 9 public class Solution {
10     public ListNode SortList(ListNode head) {
11         if (head == null || head.next == null) return head;
12         ListNode p = head, q = head;
13         while (q != null && q.next != null) {
14             q = q.next.next;
15             if (q == null) break;
16             p = p.next;
17         }
18         q = p.next;
19         p.next = null;
20         p = SortList(head);
21         q = SortList(q);
22         return mergesort(p, q);
23     }
24     public ListNode mergesort(ListNode p, ListNode q) {
25         ListNode head = null;
26         ListNode cur = null;
27         while (p != null && q != null) {
28             if (p.val < q.val) {
29                 if (head == null) head = cur = p;
30                 else {
31                     cur.next = p;
32                     cur = cur.next;
33                 }
34                 p = p.next;
35             }
36             else {
37                 if (head == null) head = cur = q;
38                 else {
39                     cur.next = q;
40                     cur = cur.next;
41                 }
42                 q = q.next;
43             }
44         }
45         if (p != null) cur.next = p;
46         else cur.next = q;
47         return head;
48     }
49 }

View Code

posted @ 2014-01-14 09:20 ying_vincent 阅读(136) 评论(0) 收藏举报

刷新页面返回顶部