Codeforces-solutions/problemlist.md

Problem List

A little collection of interesting problems that I randomly decided to do.

Ad-hoc/Greedy

• B. Gellyfish and Baby's Breath

  Cool ad-hoc problem, a little of math but mostly greedy.

• C. Ranom Numbers

  One of the most annoying problem I did, good to prepare for the future hell.

• C. Median Splits

  Another incredibly annoying problem, beware...

Data structures

• D. Recommendations

  Can be solved with two sets or binary search with sparse table.

• D. Kevin and Competition Memories

  Another interesting sparse table problem, I'm not sure it needs one, but I solved with one.

• D. R3D2 and Droid Army

  Another sparse table problem.

• E. Turn Off The TV

  Can be solved with sparse table or coordinate compression with prefix sum.

• D. CGCDSSQ

  Can be solved in two ways, but the sparse table one is interesting, although the other way seems more versatile.

Reroot

• D. Tree XOR

  Interesting reroot problem, there's not much for me to say about it.

• F. Gardening Friends

  Very standard reroot problem, but interesting as an exercise.

DP

• D. World is Mine

  It's cool to think about this problem, it has an interesting way to solve.

• D. Inversion Value of a Permutation

  Now THIS is a problem you have to think outside the box!

• F - Prefix LIS Query

  Interesting LIS problem.

• E - Knapsack 2

  Knapsack based on weight problem, classic.

• R - Walk

  Classic matrix exponentiation problem.

• Book Shop II

  Amazing knapsack problem, really satisfying to do!

• E. Xor-sequences

  An interesting way to learn how to visualize a DP as a graph and optmize it using matrix exponentiation.

• C. Gerrymandering

  A bit basic DP problem, but still interesting to think about all the possible cases and make a DP about it.

• E. Money Buys Happiness

  Cool DP problem, you have to understand knapsack to do and optmize it.

• G. Mukhammadali and the Smooth Array

  Pretty simple, but requires optmization.

• B. Jzzhu and Sequences

  Basic problem about matrix exponentation, but not as obvious.

• D. Jellyfish and Mex

  An interesting problem to think about.

• C. Lazy Narek

  I just liked the problem, not particularly hard.

• D. Maximum Subarray

  Interesting to think about the transitions and the states, although figuring out it's a dp problem is already a challenge by itself.

Graph

• D. D/D/D

  Cool graph problem, not exactly difficult, but interesting to think about it.

• C. Wonderful City

  Amazing graph/dp problem, actually interesting to think about it.

• G2. Medium Demon Problem (hard version)

  A very simple problem once you finally understand it, interesting to learn about dfs and all that.

Math

• E2. Rudolf and Snowflakes (hard version)

  Not so hard if you know how to deal with C++ or any other language with big integer, but it's interesting to think about regardless, can also be solved with a binary search, but it's not required.

• F. Expected Median

  Kinda introductory combinatory problem, but interesting as an exercise.

DSU

• https://codeforces.com/problemset/problem/1985/H1

  DSU with rollback problem, cool to think about and not really that difficult.

Bridge

• F. Non-academic Problem

  Bridge to compress the graph into a tree.

Divide and Conquer

• F. BattleCows

  Interesting problem to think about, good introduction to divide and conquer in my opinion and can be used as a bridge to segment trees.

String

• G1. Division + LCP (easy version)

  Can be solved in a lot of ways, but I find hashing with binary search simpler.