Hi! Codeforces Community. Many a times while practicing problems or in contest we get few problems that take hours of struggle but at the end leave us with something new, some brillaint concept, idea or trick. Just wanted to know about "Special Problems" that you may have come across, that had taught you something great! Please, forgive me for any mistake!

This problem (but with O(NlogN)) really helped me understand

Spoilerslope trick

This is a very novice problem that many people come across in the beginning of their journey. Basically , it asks you to compute factorials of larger numbers like

100!(No modulo, the exact no) . To solve this (C++ at least) one has to do manual multiplication on strings from 1 to n and get the final result.I found this problem quite interesting back when I was relatively new to coding.

https://www.spoj.com/problems/FCTRL2/

https://leetcode.com/problems/stone-game-v/ made me learn that sometimes recursive dp is better than iterative dp. Because in this problem the time limit was strict and while calculating answer with iterative dp we have to calculate all states which lead to TLE while in recursive dp a lot of states which were never going to be used were ignored & giving AC

https://www.spoj.com/problems/AGGRCOW/ The most popular problem taught me binary search

Looking forward to many more great problems from this blog

Problem 1

Problem 2

Problem 3

Problem 4

Problem 5

Problem 6

What are these problems based on ?

These are my starred problems. I learnt something new from them. One problem is about rerooting technique, one is modifying regular dsu a little bit, one might be small to large trick. Try these and see for yourself.

as I'm a beginner I cant give much advice on this topic I just wanted too thank you for creating such a nice blog the answers will benefit a lot of people(myself as an example)

Welcome :)

I think for me it was this one- ABC165 — C

I learnt how to use

Spoilerdfs for brute force

from this question and also the calculation for the time complexity of this question taught me about a new concept... it is called stars and sticks something. You should try this question out!