【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.

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题解：递归就可以了。

Java代码如下：

 /**
  * Definition for binary tree
  * public class TreeNode {
  *     int val;
  *     TreeNode left;
  *     TreeNode right;
  *     TreeNode(int x) { val = x; }
  * }
  */
 public class Solution {
     public TreeNode sortedArrayToBST(int[] num) {
         return Helper(num, 0, num.length-1);
     }
     public TreeNode Helper(int[] num,int begin,int end){
         if(begin > end)
             return null;

         int mid = (begin + end)/2;
         TreeNode root = new TreeNode(num[mid]);
         root.left = Helper(num, begin, mid-1);
         root.right = Helper(num, mid+1, end);
         return root;
     }
 }