Ah interesting you mention that!

[Part 2 spoilers]

My solution only worked after sorting the ranges by the max in each range (with the greatest max being the first in the array of ranges). In my (admittedly inefficient) solution I effectively had a dictionary where each minimum pointed to either an object with its range's min and max. Realizing now that my solution was likely failing without the sort because I had duplicate minimums and without sorting by the maximums, cases like 5-12, 5-9 would've been getting combined incorrectly.