<link href="//maxcdn.bootstrapcdn.com/bootstrap/3.3.0/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/3.3.0/js/bootstrap.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<div class="container">
<div class="note">
<p><b>Note : </b>Make sure you watch this in responsive after 992px it's working after this.</p>
</div>
<div class="row row-fluid">
<div class="col-xs-12 col-sm-6 col-sm-push-6 col-md-6 col-md-push-0">
<div class="a">A</div>
</div>
<div class="col-xs-12 col-sm-6 col-sm-pull-6 col-md-6 col-md-pull-0">
<div class="b">B</div>
</div>
</div>
</div>
