Pardon for the weird title.

This blog is just meant to start a discussion and question the idea of adding problems like 2132D - From 1 to Infinity into contests.

Before stating my point: This blog is not meant to target or attack any problem setter. I'm just sharing my thoughts and confusion, hoping to start a healthy discussion.

In this problem, there are basically two parts to the solution:

1) Find the last number N whose digits all belong to the first K digits and then add the first remaining digits of N + 1. (This part is relatively easier and smaller.)

2) Find the sum of the sum of digits for all numbers from 1 to N.

Now, this second task is something you can literally find on Google with one quick search. Here’s one such source:

Sum of digits from 1 to N (GFG)

And that’s where my confusion starts. What’s the point of adding such tasks to a contest when the main part of the solution is already out there and participants are allowed to use it?

Does being good at CP also mean being good at Googling standard implementations and plugging them in? I get it when it’s about common stuff like finding cycles or diameter in a tree because those are well-known techniques. But here, when the “main juice” of the problem is easily available online, isn’t it kind of unfair to people who spend time implementing it themselves compared to those who just grab it from the internet? Of course, it’s not the fault of those who use code from the internet since it’s allowed during the contest, but it still feels a bit off from a fairness perspective.

And if the real goal of the problem was just to check if you can find N, then why not directly ask for N instead of also requiring the sum of the first K digits?

I’m just genuinely confused and raising a point here. Would love to hear what others especially setters think about including such problems in contests.