leetcode - Convert Sorted List to Binary Search Tree

最新推荐文章于 2021-11-02 12:48:41 发布

转载最新推荐文章于 2021-11-02 12:48:41 发布 · 66 阅读

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原文链接：http://www.cnblogs.com/zhanghs/archive/2013/03/28/2986165.html

本文详细介绍了如何使用递归方法将一个有序链表转换为平衡二叉搜索树。通过中序遍历链表找到中间节点作为根节点，并递归地将左侧链表和右侧链表转换为子树。

题目描述：点击此处

 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 /**
10  * Definition for binary tree
11  * struct TreeNode {
12  *     int val;
13  *     TreeNode *left;
14  *     TreeNode *right;
15  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
16  * };
17  */
18 class Solution {
19 public:
20     TreeNode *sortedListToBST(ListNode *head) {
21         // Start typing your C/C++ solution below
22         // DO NOT write int main() function
23       if (head==NULL)
24         return NULL;
25       int size = 0;
26       ListNode * middle = head;
27       while (middle != NULL){
28         size++;
29         middle = middle->next;
30       }
31       size /= 2;
32       ListNode * last = NULL;
33       middle = head;
34       while (size>0){
35         last = middle;
36         middle = middle->next;
37         size--;
38       }
39       TreeNode * root = new TreeNode(middle->val);
40       if (middle != head){
41         last->next = NULL;
42         root->left = sortedListToBST(head);
43       }
44       root->right = sortedListToBST(middle->next);
45       return root;
46     }
47 };

转载于:https://www.cnblogs.com/zhanghs/archive/2013/03/28/2986165.html