leetcode 109. Convert Sorted List to Binary Search Tree

最新推荐文章于 2021-01-12 00:53:34 发布

转载最新推荐文章于 2021-01-12 00:53:34 发布 · 52 阅读

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原文链接：http://www.cnblogs.com/ym65536/p/4293776.html

本文介绍了一种将升序排列的单链表转换为高度平衡的二叉搜索树(BST)的方法。通过计算链表长度，并使用递归方式从中点构造树来实现平衡。此算法确保了BST的高度尽可能最小。

Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST.

[Solution]

 1 TreeNode *sortedListToBST(ListNode *head) 
 2     {
 3         int len = 0;
 4         for (ListNode *visit = head; visit != NULL; visit = visit->next)
 5             len++;
 6         
 7         return BSTtranslate(head, 0, len - 1);
 8     }
 9     
10     TreeNode *BSTtranslate(ListNode *head, int left, int right)
11     {
12         if (left > right)
13             return NULL;
14             
15         int middle = (left + right) / 2;
16         ListNode *visit = head;
17         for (int i = left; i < middle; i++)
18             visit = visit->next;
19             
20         TreeNode *root = new TreeNode(visit->val);
21         root->left = BSTtranslate(head, left, middle - 1);
22         root->right = BSTtranslate(visit->next, middle + 1, right);
23         
24         return root;
25     }