108 Convert Sorted Array to Binary Search Tree

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

Solution:

/**
 * 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) {
        int n = nums.size();
        if ( n == 0 ) return NULL;
        TreeNode *root = new TreeNode(nums[n/2]);
        vector<int> left(nums.begin(), nums.begin() + n/2);
        vector<int> right(nums.begin()+n/2+1, nums.end());
        root->left = sortedArrayToBST(left);
        root->right = sortedArrayToBST(right);
        return root;
    }
};

Notes
Note the syntax to create a sub-vector:

// create a vector from nums[n1] to nums[n2-1]
vector<int> left(nums.begin() + n1, nums.begin() + n2);