LeetCode题解之Convert Sorted List to Binary Search Tree

1、题目描述

2、题目描述

使用快慢指针寻找链表中间值。

 

3、代码

 1 TreeNode* sortedListToBST(ListNode* head) {
 2         if (head == NULL)
 3             return NULL;
 4         
 5         ListNode *mid = findmid(head);
 6         
 7         TreeNode *node = new TreeNode(mid->val);
 8         
 9         if (head == mid)
10             return node;
11         
12         node->left = sortedListToBST(head);
13         node->right = sortedListToBST(mid->next);
14         return node;
15         
16     }
17     
18    
19     
20     ListNode *findmid(ListNode* left)
21     {
22         ListNode *preptr = NULL;
23         ListNode *slow = left;
24         ListNode *fast = left;
25         
26         while (fast != NULL && fast->next != NULL) {
27             preptr = slow;
28             slow = slow->next;
29             fast = fast->next;
30             fast = fast->next;
31         }
32         if (preptr != NULL)
33             preptr->next = NULL;    
34         return slow;
35     }
36

 

posted @ 2019-02-25 21:55  山里的小勇子  阅读(90)  评论(0)  编辑  收藏  举报