leetcode 108

/**
 * 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* sortedArrayToBST(vector<int>& nums) {
        return sortedArrayToBST(nums, 0, nums.size() - 1);
    }
private:
    TreeNode* sortedArrayToBST(vector<int> &nums, int start, int end)
    {
        if (start > end)
        {
            return NULL;
        }

        int mid = (start + end) / 2;
        TreeNode* node = new TreeNode(nums[mid]);
        node->left = sortedArrayToBST(nums, start, mid - 1);
        node->right = sortedArrayToBST(nums, mid + 1, end);
        return node;
    }
};