123gjweq2's blog

By 123gjweq2, history, 21 month(s) ago, In English

What is your least favorite type of problem / least favorite topic? I personally do not like graph problems.

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21 month(s) ago, hide # |
 
Vote: I like it +69 Vote: I do not like it

Constructive. If every problem was constructive, i'd probably be a pupil

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    21 month(s) ago, hide # ^ |
     
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    Same. I would say constructive too, but it becomes my favorite problem type after I manage to solve one by myself.

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    21 month(s) ago, hide # ^ |
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    spoiler
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    21 month(s) ago, hide # ^ |
     
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    Can you define what a "constructive problem" is to you? The people that I've talked to about this don't have nearly the same opinion as I do.

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      21 month(s) ago, hide # ^ |
      Rev. 2  
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      Questions like these where you just have to think of a pattern
      https://mirror.codeforces.com/contest/1930/problem/B
      https://www.codechef.com/problems/STACKED

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        21 month(s) ago, hide # ^ |
         
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        I agree that it's fair to call those problems constructive. For the first one you can simply try all the common answers for the problem and one of them works.

        1 2 3 4 5 ...

        1 N 2 N-2 3 N-3 ...

        N-1 N-2 N-3 ...

        etc

        The main observation being that the smallest multiple of x that isn't x is 2x. Trivial observations are easy to miss and I didn't think of that until finding the construction.

        The second seems to be a mix of greedy thinking (use big numbers to escape the sum range when you get to it) and a well known greedy problem (with numbers [1,x] you can always find a subset of sum for every value in [0, 1+2+3+...+x]). I've seen easier problems in div1E.

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      21 month(s) ago, hide # ^ |
       
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      I would describe as "problems in which you're given a set of properties and aims to find a structure that matches them"

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        21 month(s) ago, hide # ^ |
         
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        I don't agree. It depends on the solution. For example: if the solution is some DP then DP is the main part of the problem.

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    21 month(s) ago, hide # ^ |
     
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    Same man. It is like a luck thing. Either you get the pattern or not.

    Spoiler
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      21 month(s) ago, hide # ^ |
       
      Vote: I like it +1 Vote: I do not like it

      There more general ideas that motivate constructives than you think once you start reflecting more and put extra effort in trying different approaches. This is coming from someone that is specifically solving more constructives to do better in contests. Sadly something that is necessary to improve on (with pain in the process), but I think being more open minded on this type of problem helped my solving.

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        21 month(s) ago, hide # ^ |
         
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        True that. I have realized that I should stop whining and get better. Will practice such problems more, hopefully. Thanks a lot for the advice! :)

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      21 month(s) ago, hide # ^ |
       
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      It is more of an IQ thing than a luck thing.

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    21 month(s) ago, hide # ^ |
     
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    I get where you are coming from, but I have a well respected teacher, who says that a person who can solve a 3500 rated dp/ds but can't do 3400 constructives, you're doing something wrong.

    [This is a personal opinion from me, not my teacher]: Constructives force you don't think to solve the problem in known or standard ways, rather forces you to think differently and out of the box; yes it can be frustrating but when you're trying a constructive problem, your brain thinks of 1000 different new/cool/weird ideas + observations + etc which can come very helpful in the future problems, and it also boosts your creativity

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    21 month(s) ago, hide # ^ |
     
    Vote: I like it -8 Vote: I do not like it

    I used to dislike constructive problems too, but from a certain point on, I just started enjoying how most of them rely on simple patterns.

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    21 month(s) ago, hide # ^ |
     
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    I am also very weak and get stuck on every easy constructive problems. But I still like them most.

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21 month(s) ago, hide # |
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1995C - Squaring

1995B2 - Bouquet (Hard Version)

these are worst type of problem that I could imagine.

specifically problem using formula/math problem, like translate problem statement and then answer be like one line max(0, c[i-1] + ceil(log2(log2(a[i-1])/log2(a[i])))) * (k1-r)*x+(k2+r)*(x+1) where k1=min(c_x,m/x) and k2=min(c_{x+1},c/(x+1)) .. it's fucking insane actually

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    21 month(s) ago, hide # ^ |
     
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    Nah, maybe the formula should actually be:

    c[i]=max(0,c[i-1]+ceil(log2(log2(a[i-1])/log2(a[i]))))

    272232560

    why are you multiplying it with (k1-r)*x+(k2+r)*(x+1)? I believe there's no need.

    It's not hard it's just math.

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21 month(s) ago, hide # |
 
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Graph, data structures and implementation

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    21 month(s) ago, hide # ^ |
     
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    I feel like implementation-heavy ones are fine unless you gotta implement them in a language other than python.

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      21 month(s) ago, hide # ^ |
       
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      I dislike them for lacking some brilliant ideas(for the most part) and just being about writing a bunch of code

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      21 month(s) ago, hide # ^ |
       
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      I feel like implementation-heavy ones are fine unless you gotta implement them in a language other than C++.

      don't get me wrong, I've done python for 2 whole years, but not for cp, for projects, my whole github is python-based, but for cp I'd rather do C++ A hundred times, You know, if you learn it you'll love it, the problem is everywhere u go they try to teach the things that are useful in projects, never in cp; but learning C++ for cp is easy and almost super fast(nearly my whole class did in like a week at max), so yeah C++ is the one for cp, at least for me

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21 month(s) ago, hide # |
 
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I don't like constructive ones

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21 month(s) ago, hide # |
 
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hard problems, but seriously, heavy implementation

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Vote: I like it +129 Vote: I do not like it

I don't usually hate problems, I hate badly-written tutorials.

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21 month(s) ago, hide # |
 
Vote: I like it +7 Vote: I do not like it

I hate bitmask problems.

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Vote: I like it +5 Vote: I do not like it

implementation

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21 month(s) ago, hide # |
 
Vote: I like it +59 Vote: I do not like it

Problems with no thinking or brute forcing and noticing a pattern which 99% of participants can't prove.

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Vote: I like it +58 Vote: I do not like it

Geometry.

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Vote: I like it -18 Vote: I do not like it

interactive...

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Vote: I like it -8 Vote: I do not like it

Constructive and matrix implementation stuff

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combinatorics and number theory

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Vote: I like it +6 Vote: I do not like it

now that i think about this i only hate problems that are hard to implement i really never mind the topic i sometimes even solve geometry ...

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number theory

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Vote: I like it +6 Vote: I do not like it

DP: specifically plug, digit, bitmasks, and those where you have a complicated state and transition which often involve math.

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Vote: I like it +59 Vote: I do not like it

bitset

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Ad-hoc

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21 month(s) ago, hide # |
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Graph, problems with segment-tree/sqrt-decomposition and problems with fractional numbers.

Edit: And yeah, the most important. Games.

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21 month(s) ago, hide # |
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Vote: I like it +3 Vote: I do not like it

Problems that are stolen from other sources

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Vote: I like it +110 Vote: I do not like it

problems that i can't solve

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Constructive/ad-hoc/guessing problems. Or when the proof is harder than the problem.

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21 month(s) ago, hide # |
 
Vote: I like it +45 Vote: I do not like it

Ad-hoc problems in general.

Especially problems where you are given an array (or a binary/ternary/etc. string) and are asked to find the minimum number of operations to make the array satisfy a certain condition.

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    21 month(s) ago, hide # ^ |
     
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    Agree with you, sometime I think I was the most stupid person in the world because of not solving that problems :(((, maybe every problems like that

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Data Structures.

When I'm coding for myself I love DS. When I'm coding for a contest I hate DS.

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  1. Problems with lots of corner cases that can't be generalized and require writing several huge IFs before\after core algorithm.
  2. Problems where author expects people to solve it using a math formula\dp\something clever, but due to constraints it's possible to write a bruteforce solution in C++ (but not in other languages) which invalidates the whole point of the problem.
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21 month(s) ago, hide # |
 
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Graph problems really piss me off.

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21 month(s) ago, hide # |
 
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Constructive problems first of all

Guess problems ( I mean not all of them are bad. If some observations lead you to the guess then this type of problem is fine. )

And math problems that are more suited for IMO or national mathematical rounds and you need to have knowledge of some theory that barely anyone knows.

And finally single trick pony problems (If you know it then you can solve it in 5 minutes. Otherwise good luck)

:v

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    21 month(s) ago, hide # ^ |
     
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    you need to have knowledge of some theory that barely anyone knows.

    Yeah I one time saw a problem that required knowledge of "the toilet function" or something. They're really running out of names for these arcane math things.

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21 month(s) ago, hide # |
 
Vote: I like it +8 Vote: I do not like it

Greedy+Games. With my slow brain and deterministic mindset combined, it's really hard to come up with an idea, assure that it would be correct, and keep that assurance solid enough so my mind could force itself to write the code. Or I'm just bad in heuristics-based stuff. :<

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Problems that have strings or game theory. I always get super confused thinking about cases in Alice Bob problems.

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Vote: I like it +18 Vote: I do not like it

Anything that doesn't even slightly resemble a real world process.

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Vote: I like it +14 Vote: I do not like it

constructive problems , especially the ones which you need to generate a permutation which satisfies a random constraint

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Vote: I like it +3 Vote: I do not like it

Casework problems.

Imagine

Just.. ewww.

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21 month(s) ago, hide # |
 
Vote: I like it +3 Vote: I do not like it

Those problems whose logic is pretty simple but have annoying edge-cases. Simple problems with many cases to consider and there is no pattern to use loop.

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Geometry + Constructive + implementation

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Constructives are the reason of me tanking the contest at which they appear especially at C.

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brute force and greedy.

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Greedy

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Vote: I like it +3 Vote: I do not like it

Games and number theory

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Geometry is shit

Dp Is Shit

Case work is Shit

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Constructive, combinatorics and very gross math problems

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Vote: I like it +21 Vote: I do not like it

long code problems

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ad-hoc stuff where 90% of the time the solution is guessable

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Vote: I like it +30 Vote: I do not like it

I think the problems I like the least are problems that have way too much emphasis put on knowing some (relatively) hard algorithm or data structure, and otherwise the problem is pretty easy. This is even worse when such problems appear in onsite contests without internet access.

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21 month(s) ago, hide # |
 
Vote: I like it +3 Vote: I do not like it

geometry

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dp+graphs... i love dp ...but when it gets merged with graphs i just hate it

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I hate sigma problems.

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Vote: I like it +20 Vote: I do not like it

String, heavy DS, heavy math

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Math or data structures:(

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Vote: I like it +2 Vote: I do not like it

Probability

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Vote: I like it +4 Vote: I do not like it

for me its number theory

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dp

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1) Implementation heavy problem. (probably too many corner case are not my type.)
2) Every problem that require reconstruct the operations / rebuild the graph, rather than just asking number of operation.
may be, i am just saying all kind of problems i am weak at/

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i like tree, actually i like everything but i m just stupid

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Data Structures , Math

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Vote: I like it -7 Vote: I do not like it

graph

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Math problems, especially where solution time complexity is less than O(N), they are usually hard or you just have to know some specific math to solve them

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18 months ago, hide # |
 
Vote: I like it +3 Vote: I do not like it

proof by AC problems.

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18 months ago, hide # |
 
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least favorite type of problem: easy problems which should be solved, but was unable to solve during contest..

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18 months ago, hide # |
 
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graph theory by far

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ad-hoc, there could be so non-straightforward things

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    18 months ago, hide # ^ |
     
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    idk if I'm just stupid, but I've only seen 1 straightforward codeforces problem in my entire life

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      18 months ago, hide # ^ |
       
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      They've put standards pretty high like TC — that's tough optimization stage, you may find out that HackerEarth on the early stages provided tasks where you have no clue what is required

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18 months ago, hide # |
 
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interactive.How can I solve problems better than a robot?

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eeeeeeeeeeeeeeeeeeeeeasy to come up with the solution but diiiiiiiiiiiiiiiiiiiiiiiiiiiiifficult to write the code

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Ad-hoc

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I hate -... .. — .-- .. ... . / .- -. -.. / --. .-. .- .--. .... / — .... . — .-. -.--

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18 months ago, hide # |
 
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I don't like geometry.

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math and DP