[LeetCode108] Convert Sorted Array to Binary Search Tree

题目：

Given an array where elements are sorted in ascending order, convert it to a height balanced BST.

分类：Tree Depth-first Search

代码：

 1 /**
 2  * Definition for a binary tree node.
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */
10 class Solution {
11 private:
12     
13 public:
14     TreeNode* sortedArrayToBST(vector<int>& nums) {
15        return helper(nums, 0, nums.size() - 1);
16     }
17     
18     TreeNode* helper(vector<int>& nums, int begin, int end)
19     {
20         if(begin > end)
21             return nullptr;
22         int mid = begin + (end - begin) / 2;
23         TreeNode* root = new TreeNode(nums[mid]);
24         root->left = helper(nums, begin, mid - 1);
25         root->right = helper(nums, mid + 1, end);
26         return root;
27     }
28 };

 

posted @ 2016-08-15 11:16  zhangbaochong  阅读(229)  评论(0)    收藏  举报