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:
TreeNode *generate(vector<int> &num,int left,int right){
if(left > right) return NULL;
int mid = (left + right) / 2;
TreeNode *tleft = generate(num,left,mid - 1);
TreeNode *tright = generate(num,mid + 1,right);
TreeNode *root = new TreeNode(num[mid]);
root -> left = tleft;
root -> right = tright;
return root;
}
TreeNode *sortedArrayToBST(vector<int> &num) {
int len = num.size();
return generate(num,0,len - 1);
}
};