The given tree is not balanced!

#1

Why for the input A : [ 1, 4, 8 ] , the output is shown as:
The given tree is not balanced!
How to debug it here.

#2

This code works well for all cases.


void bst(const vector<int> &A,TreeNode* &ans, int l,int r )
{
    if(l>r)
        return;
    int mid= (l+r)/2;
        
    ans = new TreeNode(A[mid]);
    
    bst(A, ans->left, l,mid-1);
    bst(A, ans->right, mid+1,r);

}

TreeNode* Solution::sortedArrayToBST(const vector<int> &A) {
    
    int l = 0;
    int r = A.size()-1;
    TreeNode* ans;
    
    bst(A, ans,l,r);
    return ans;
}