I really want to know whats the difference between 2 types of lower_bound? 1) lower_bound(st.begin(), st.end(), val) and 2) st.lower_bound(val). As you can see in 28778333 and 28778499 the second type is much much faster!

There are lots of problems on CF and it's really hard for me to find problems that are interesting and I can solve them with my programming knowledge! Can you please share the problems that you have seen and they don't really want a high programming knowledge and they are more theoretical? (harder problems are more interesting!)