I am not any expert in competitive programming, so this post is not about teaching you fellow coders any new things that you already don't know. Rather I am asking you high rated Div. 1 people to share your experience, problem solving approach of using STL(vector, pair, queue, priority queue, stack, set, map, algorithm) for good understanding of when and where to use STL.

I have already read the various STL tutorials on Topcoder(by DmitryKorolev): STL Tutorial 1 STL Tutorial 2

Codeforces: DFS using STL by evandrix

But after reading these I found out that they are just meant for giving you some basic understanding of "What is STL and its importance". These were very informative, but not so much helpful for contest programming as they didn't gave any practical idea or insight of in which cases a programmer should go for which STL.

I have very little experience of contest participation but in this short duration I went through codes of various people to learn their way of coding. There I found out that there is a powerful feature of the Standard Template Library (STL) – a great tool that, sometimes, can save you a lot of time in an algorithm competition. I learned that some people often have very short solutions by using the STL. Due to this they are able to write and submit their codes very fast. e.g.

vjudge3's pair usage for 297C - Splitting the Uniqueness

Mr.'s map, pair usage for 402B - Trees in a Row

Rebryk's queue usage for 371B - Fox Dividing Cheese

while for the same problem 404C - Restore Graph ig_dug's vector, pair and kaushik90's easy vectors

Above all I found that I was always relying on using arrays and due to this it was very difficult for me to handle the data and consequently I was not able to implement my approach. One more problem I felt later that I was confused for Which STL should I select for a given problem scenario. It happened at times that I needed pair but I was using two separate vectors.

So in the end I am requesting and inviting codeforces community to share their experiences of effective usage of STL for fast and short code writing. It would be very much benefiting if in your replies you explain your way of thinking in the perspective of using STL, Please explain how do you choose the appropriate STL(as in my case of confusion of selecting pair or 2 vectors) in the contest problem theory. If you want then you can cover all the STLs or you cover just one STL feature, but cover it with good explanation, examples and in detail.

This will really help the new learners.

Thanks. Happy solving.