"Conclusion" porblems refer to problems which you may think a lot for a "conclusion" but the codding is very easy. For example, 1919A - Wallet Exchange, 1919B - Plus-Minus Split, 1919C - Grouping Increases, 1919D - 01 Tree and so on.
I am very confused about these problems. Almost always, I'm struggling on one of these problems (maybe C or D or even B in a Div.2 contest). I cannot find such "conclusion" quickly. How can I improve?
Spoiler
Do you mean problems that seems difficult, or with long solution, but can be solved in much easy way? Because I don't get what do you mean by "conclusion" problems
Honestly, I don't think there's much good advice beyond "solve more problems" and "try not to overthink if it's div2A".
Also, can you tell me how to implement 1919D - 01 Tree since you said you found it easy to code? I spent quite some time while coding it :p
The first implementation described in the editorial is relatively messy (i.e., I think it's normal to get stuck). The linear solution requires a small extra step, but imo it's much easier to implement.
Don't actually delete the elements, just assume they are deleted from the largest to the smallest. Now, for each element, you have to find the closest "alive" elements when it's its turn to be deleted. It's equivalent to finding the nearest smaller elements on the left and on the right.
I actually implemented the linear solution in $$$O(n \log n)$$$ because it's even shorter.
orz, thank you very much