【leetcode刷题笔记】Convert Sorted Array to Binary Search Tree

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

---

 

题解：递归就可以了。

Java代码如下：

 1 /**

 2  * Definition for binary tree

 3  * public class TreeNode {

 4  *     int val;

 5  *     TreeNode left;

 6  *     TreeNode right;

 7  *     TreeNode(int x) { val = x; }

 8  * }

 9  */

10 public class Solution {

11     public TreeNode sortedArrayToBST(int[] num) {

12         return Helper(num, 0, num.length-1);

13     }

14     public TreeNode Helper(int[] num,int begin,int end){

15         if(begin > end)

16             return null;

17         

18         int mid = (begin + end)/2;

19         TreeNode root = new TreeNode(num[mid]);

20         root.left = Helper(num, begin, mid-1);

21         root.right = Helper(num, mid+1, end);

22         return root;

23     }

24 }