Prefer vector over linked lists like data structs.

[shahzadlone]

std::map, std::unordered_map, std::array and etc. are all under the hood using linked list, this slows does the program quite a lot.

Here is a beautiful video that talks about these in more depths!
https://www.youtube.com/watch?v=fHNmRkzxHWs&t=41m41s

Bonus: Even Bjarne Stroustrup recommends to only use vectors :).

Chances are we can make a better data structure (class) than the old linked list implementations of standard lib.