leetcode[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.

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