>They just told you how to solve it. But I can't see how they approach to get the answer. I think that part is the most interesting and valuable part for non-talent like me.

I ran into this too when I was preparing for a loop, especially for more complicated DP and recursion problems.

I found a website called gorecursion [0] on Reddit and he is very good at describing these solutions from the naive case to the optimized case very well. This helped me quite a bit, but I still didn't get the offer.

[0]: http://www.gorecursion.com/