Leetcode: Convert Sorted Array to Binary Search Tree

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

 1 /**
 2  * Definition for binary tree
 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 public:
12     TreeNode *sortedArrayToBST(vector<int> &num, int start, int end)
13     {
14         if (start > end)
15             return NULL;
16         int mid = start + (end - start)/2;
17         TreeNode* node = new TreeNode(num[mid]);
18         node -> left = sortedArrayToBST(num, start, mid-1);
19         node -> right = sortedArrayToBST(num, mid+1, end);
20         
21         return node;
22     }
23     
24     TreeNode *sortedArrayToBST(vector<int> &num) {
25         // Start typing your C/C++ solution below
26         // DO NOT write int main() function
27         int start = 0;
28         int end = num.size()-1;
29         return sortedArrayToBST(num, start, end);
30     }
31 };

 

posted @ 2013-05-01 16:30  caijinlong  阅读(122)  评论(0)  编辑  收藏  举报