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

TreeNode *createSearchTree(vector
     
      & num, int left , int right){    if(left > right) return NULL;    int mid = (left+right)>>1;    TreeNode *root = new TreeNode(num[mid]);    root->left = createSearchTree(num,left,mid-1);    root->right = createSearchTree(num,mid+1,right);    return root;}TreeNode *sortedArrayToBST(vector
      
        &num) {    return createSearchTree(num,0,num.size()-1);}