css交替的循环要怎么写

请问类似以下的css交替的循环要怎么写呀？

条件要怎么判断？

{module module=news catid=14 order=updatetime num=6}
第1条：
<div class="tu tr1">
                            <div class="img tr1 item23" data-original="{dr_thumb($t.thumb,0,0)}" style="background:url({HOME_THEME_PATH}fenzhan/images/zhan.jpg) no-repeat center/cover">
                                <img src="{HOME_THEME_PATH}fenzhan/images/ling01.png" style="max-width:100%">
                            </div>
                        </div>
第2条：
 <div class="text">
                        <div class="zhe">
                            <img src="images/ling01.png" style="max-width:100%">
                        </div>
                        <div class="zibox">
                            <div class="tou overflow" title="">地铁4号线</div>
                            <div class="zi overflow"></div>
                        </div>
                    </div>
{/module}