jquery to position elements randomly, but without overlap

I am placing a dynamic amount of elements in random positions in a parent element. Each element is 75px square and position:absolute and I'd like to make sure that their random x and y co-ordinates don't overlap those of any already positioned elements.

Points for urgency...

$('.className').each(function(){
$(this).css({ 'top':randomXToY(0,375),
	 'left': randomXToY(0,450),
	});
});
 
// in case it's useful, my random function is just:
 
function randomXToY(minVal,maxVal,floatVal){
  var randVal = minVal+(Math.random()*(maxVal-minVal));
  return typeof floatVal=='undefined'?Math.round(randVal):randVal.toFixed(floatVal);
}

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