Can you suggest any resources to freshen up on big o notation and fundamental data structures & algorithms that are not academically dense (i.e CLRS)?

I'm currently working through Cracking the coding interview & Elements of programming interviews but I really need to revisit the fundamentals, specially recurrence relations and calculating the order of complexity for an algorithm but I can't find any resources that are not too academically verbose, I have a really hard time reading mathematical notation.