dynamically created bootstrap columns with different heights, float to left - css

Question

Consider an unknown number of divs being created dynamically and styled using the bootstrap grid system. In this example, I'm using col-sm-4 so after every third block, we move to a new row. The blocks (divs) can be different heights, which is determined by the content within.
This is where I run into the layout problem. When moving to a new row, I want the fourth block to float to the left. This only happens when the left most div in the row above is also the shortest. I have pictures to illustrate.
Real Life:
The Dream:
The "correct" way to do this would be to wrap every three in a row class I beleive, but I'm not sure how to do this with dynamic content (could probably hack it) or if there's an easy css solution.
HTML:
<div class="row">
<div class="col-sm-12">
<div class="col-sm-4 block">
<div class="inner-block"></div>
</div>
<div class="col-sm-4 block">
<div class="inner-block"></div>
</div>
<div class="col-sm-4 block">
<div class="inner-block" style="height:150px"></div>
</div>
<div class="col-sm-4 block">
<div class="inner-block"></div>
</div>
</div>
</div>
CSS:
.block {
padding: 5px;
}
.inner-block {
height: 200px;
background-color: blue;
}
Plunker Example (expand preview to proper size)

Answer 1

If your system is unable to add first/last classes on every nth div, then you can use the nth-child css pseudo selector.
#media (min-width: 768px) {// For medium displays and above
.col-sm-4:nth-child(3n+1) { // We target every 3rd div but offset the count by 1 so that that 1st, 4th 7th etc divs are cleared
clear:both; // Clear the float
}
}