目标类在父类中的最后一个实例

I have said divs:

我有div说:

<div>
    <div class="p1"></div>
    <div class="p2"></div>
    <div class="p1"></div>
    <div class="p2"></div>
</div>
<div>
    <div class="p1"></div>
    <div class="p2"></div>
    <div class="p1"></div>
    <div class="p2"></div>
</div>
<div>
    <div cl