Cooper1214's blog

"Drop your Favorite Problems" thread with the rating of <=1700
By Cooper1214, 21 month(s) ago, In English

Hi,
Drop some of your favorite problems which you think can educate us some new concept, tricks or ideas and we have a take away from those problems. :)
Please try to follow this particular format so that it is helpful for the readers (and also to me):

Probelm Rating (Eg: 1500) :
- Problem 1 (Why you recommend this problem)
- Problem 2 (Why you recommend this problem)
Probelm Rating 2 (Eg: 1600) :
- Problem 1 (Why you recommend this problem)
- Problem 2 (Why you recommend this problem)

You can also drop problems without following this xD. Just don't forget to drop some cool problems which we should definitely practice. :)

  • Vote: I like it
  • +22
  • Vote: I do not like it

Comments Comments (25)
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21 month(s) ago, # |
← Rev. 2   Vote: I like it +9 Vote: I do not like it

(https://mirror.codeforces.com/problemset/problem/1519/D)

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21 month(s) ago, # |
  Vote: I like it 0 Vote: I do not like it

Even Subarrays

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21 month(s) ago, # |
← Rev. 2   Vote: I like it +19 Vote: I do not like it

1770C - Koxia and Number Theory 1801A - The Very Beautiful Blanket

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21 month(s) ago, # |
← Rev. 3   Vote: I like it -10 Vote: I do not like it

https://mirror.codeforces.com/contest/1731/problem/D DP/Prefix sums/Sparse table/Segment tree + binary search

Brothers, / equals or in my description, the problem is mostly solved with very easy techniques.

It is 1700 rated problem, why downvotes?

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    21 month(s) ago, # ^ |
    ← Rev. 2   Vote: I like it +2 Vote: I do not like it

    I Like the Problem mentioned above and recommend you all to solve both problems.

    486E- LIS of Sequence

    Good dp Problem. It will strengthen your concept of LIS.

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21 month(s) ago, # |
← Rev. 6   Vote: I like it +1 Vote: I do not like it

https://mirror.codeforces.com/contest/1805/problem/D I think that's a really good problem because it greatly improves your bfs realisation skills. And it also includes a lot of concepts that are oftenly used in a lot of problems related to bfs/dfs. So i think it's a really great problem to practice on

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

Some problems that I really enjoyed solving and found enlightening. They made me very happy when I got AC:

dp
graphs
binary search
greedy
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21 month(s) ago, # |
  Vote: I like it 0 Vote: I do not like it

https://mirror.codeforces.com/contest/1594/problem/D A very great DSU problem

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

https://mirror.codeforces.com/problemset/problem/382/C

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21 month(s) ago, # |
  Vote: I like it -10 Vote: I do not like it

1734D — Slime Escape

a problem which took 7 months for me to upsolve

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

Air Conditioner — great DP

Pair of Topics — the 2 pointer trick is pretty neat

Most of my favorite problems are 2000 so I don't have much to share

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21 month(s) ago, # |
  Vote: I like it +2 Vote: I do not like it

https://mirror.codeforces.com/contest/1373/problem/D

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

CF 1695C Zero Path

CF 1497 C2 k-LCM (hard version)

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21 month(s) ago, # |
← Rev. 2   Vote: I like it +1 Vote: I do not like it

I like this one:

1699C — The Third Problem

Not the most creative name but its solution is satisfying.

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21 month(s) ago, # |
← Rev. 3   Vote: I like it +1 Vote: I do not like it

Some problems are not <= 1700, but I think they are very interesting.

My favorite DP problems:

Hint
Hint

My favorite Graph problems: - 1675F - Vlad and Unfinished Business — Easy problem, but you need to think a bit to solve it

Hint
Hint
Hint

Other: - 455D - Serega and Fun — SQRT decomposition

Hint

My english is not very good so I could write something wrong.

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

1538D — Another Problem About Dividing Numbers
Because it's the first 1700 problem I solved during live contest. Also its a pretty cool number theory problem.

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21 month(s) ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

These are some of my favorite recent problems with rating 1300-1700.

  • 1698C (1300) Observation from the tutorial was so mind-blowing to me so I remembered this problem.
  • 1748B (1400) I like this problem because it uses pigeonhole principle.
  • 1772D (1400) This is the problem from which I have learned the power of maintaining the lower bound and upper bound for something that can have multiple possible values.
  • 1796C (1600)
  • 1777C (1700) This problem is on this list because it's very educational.
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21 month(s) ago, # |
  Vote: I like it +1 Vote: I do not like it
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21 month(s) ago, # |
← Rev. 3   Vote: I like it +1 Vote: I do not like it

1707A - Doremy's IQ

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21 month(s) ago, # |
← Rev. 4   Vote: I like it +1 Vote: I do not like it

Recent problem.It is enough to learn digit dp well. 1808 C — Unlucky Numbers

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

C. Equal Frequencies -> 1600

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