In school? You mean you went through a cs degree program without once being being asked how long an sort routine would take if you somehow needed to sort a trillion items vs sorting just 100, or maybe just one, or why nested for loops are a bad thing,, or that binary trees are amazing? If this is true, then that institution should be banned from teach cs.

You just do a quick google search:

Algorithm complexity.

That should turn up some sufficient resources to help you.

The basis are not that hard. The real stuff that you probably don't need for interviews involve a quite a bit of math. The basics are just general concepts that involve a bit of arithmetic and algebra level math. You can probably avoid the math and just learn the basics.