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

解题思路：

首先要理解，什么叫做height balanced BST ，然后就十分容易了，JAVA实现如下：

public TreeNode sortedArrayToBST(int[] nums) {		return sortedArrayToBST(nums, 0, nums.length - 1);	}	static public TreeNode sortedArrayToBST(int[] nums, int begin, int end) {		if (begin>end)			return null;		TreeNode root = new TreeNode(nums[(begin+end) / 2]);		root.left=sortedArrayToBST(nums,begin,(begin+end) / 2-1);		root.right=sortedArrayToBST(nums,(begin+end) / 2+1,end);		return root;	}