Use nested inline if-then statements (Ternary Operators)
<div ng-class=" ... ? 'class-1' : ( ... ? 'class-2' : 'class-3')">
for example :
<div ng-class="apt.name.length >= 15 ? 'col-md-12' : (apt.name.length >= 10 ? 'col-md-6' : 'col-md-4')">
...
</div>
And make sure it’s readable by your colleagues 🙂