var countNodes = function(root) {
if (root == null) return 0;
let l = root, r = root;
let lh = 0, rh = 0;
while (l != null) {
l = l.left;
lh++;
}
while (r != null) {
r = r.right;
rh++;
}
if (lh === rh) {
return Math.pow(2, lh) - 1;
}
return 1 + countNodes(root.left) + countNodes(root.right);
};