leetcode Convert Sorted Array to Binary Search Tree 树

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

把一个有序的数组编程平衡二叉搜索树。

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
	TreeNode*createTree(vector<int>&nums, int left, int right)
	{
		if (left > right) return NULL;
		int mid = (left + right) / 2;
		TreeNode *leftnode = createTree(nums, left, mid - 1);
		TreeNode *rightnode = createTree(nums, mid+1,right);
		TreeNode *node = new TreeNode(TreeNode(nums[mid]));
		node->left = leftnode;
		node->right = rightnode;
		return node;
	}
	TreeNode* sortedArrayToBST(vector<int>& nums) {
		return createTree(nums, 0, nums.size() - 1);
	}
};