Happy International Labour Day to all the hardworking contestants and problem setters!

Hello, Codeforces community! I'm glad to invite you to the Replay of IUT 11th National ICT Fest Programming Contest 2024 which will be held on May 01, 2024, at 15:00 +0600 and will run for 05 hours.

The contest will take place at Toph.co

This is not a rated contest. You can register for the contest here.

Problems of this contest were prepared and tested by upobir, ash_98, CLown1331, border, curly_braces, Hasinur_, hjr265, I_See_You, ishtupeed, mainstring, ovis96, rebornplusplus, rifatrraazz, Joty, BumbleBee, steinum, TamimEhsan, TarifEzaz, and me.

Thanks to TarifEzaz for his unconditional support and hjr265 for the best contest programming platform in Bangladesh.

We're inviting you all to participate in this contest. Hope you will enjoy the problem set. There will be an editorial for this contest shortly after the round ends.

Contest Link: Replay of IUT 11th National ICT Fest Programming Contest 2024

Happy Coding!

Hello, Codeforces community!
I'm glad to invite you to Criterion 2022 Round 15 which will be held on February 25, 2022, at 20:30 +0600 and will run for 2 hours 30 minutes.

The contest will take place at Toph.co

This contest is rated for all participants. You can register for the contest here.

Problems of this contest were prepared and tested by curly_braces, jAckAL_1586, adnan_toky, TarifEzaz, ishtupeed, ihumaunkabir and me.

Thanks to TarifEzaz for his unconditional support and hjr265 for the best contest programming platform in Bangladesh.

We're inviting you all to participate in this contest. Hope you will enjoy the problem set.
There will be an editorial for this contest shortly after the round ends.
Feel free to share your experience with previous Criterion Rounds!

Contest Link: Criterion 2022 Round 15

Happy Coding!

16th of December, 2021 is the 50th Victory day of Bangladesh!

Hello, Codeforces community! I'm glad to invite you to the Replay of Ada Lovelace National Girls' Programming Contest 2021 which will be held on December 16, 2021, at 10:00 +0600 and will run for 05 hours.

The contest will take place at Toph.co

This is not a rated contest. You can register for the contest here.

Problems of this contest were prepared and tested by Shefin_, rebornplusplus, curly_braces, adnan_toky, Abdur_Rahman_Shajib, tahsin_protik, farabi_Shafkat, rifatrraazz, ash_98, ishtupeed, TarikHassan, nahidhasan98,S.R.Shuvon, Joty, TarifEzaz and me.

Thanks to TarifEzaz for his unconditional support and hjr265 for the best contest programming platform in Bangladesh.

We're inviting you all to participate in this contest. Hope you will enjoy the problem set. There will be an editorial for this contest shortly after the round ends.

Contest Link: Replay of Ada Lovelace National Girls' Programming Contest 2021

Happy Coding!

Hello, Codeforces community! I'm glad to invite you to the Replay of Ada Lovelace National Girls' Programming Contest 2021 — Preliminary which will be held on December 02, 2021, at 18:00 +0600 and will run for 05 hours.

The contest will take place at Toph.co

This is not a rated contest. You can register for the contest here.

Problems of this contest were prepared and tested by upobir, YouKn0wWho, Shefin_, rebornplusplus, curly_braces, Abdur_Rahman_Shajib, jAckAL_1586, Joty, TarifEzaz, rifatrraazz, tahsin_protik, Fiction, TarikHassan, S.R.Shuvon, Noman_Ahmmed and me.

Thanks to TarifEzaz for his unconditional support and hjr265 for the best contest programming platform in Bangladesh.

We're inviting you all to participate in this contest. Hope you will enjoy the problem set. There will be an editorial for this contest shortly after the round ends.

Contest Link: Replay of Ada Lovelace National Girls' Programming Contest 2021 — Preliminary

Happy Coding!

Hello, Codeforces community! I'm glad to invite you to the Replay of National Girls' Programming Contest 2021 which will be held on November 28, 2021, at 18:00 +0600 and will run for 05 hours.

The contest will take place at Toph.co

This is not a rated contest. You can register for the contest here.

Problems of this contest were prepared and tested by upobir, YouKn0wWho, Shefin_, ovis96, rebornplusplus, curly_braces, adnan_toky, Asaduzzaman Herok, ash_98, Abdur_Rahman_Shajib, CLown1331, Hasinur_, hjr265, Humaun kabir, ishtupeed, jAckAL_1586, mainstring, Joty, TarifEzaz, rifatrraazz, tahsin_protik, TarikHassan, gola and me.

Thanks to TarifEzaz for his unconditional support and hjr265 for the best contest programming platform in Bangladesh.

We're inviting you all to participate in this contest. Hope you will enjoy the problem set. There will be an editorial for this contest shortly after the round ends.

Contest Link: Replay of National Girls' Programming Contest 2021

Happy Coding!

Hello, Codeforces community!
I'm glad to invite you to Replay of PIHACKS'21-CodeJam which will be held on August 05, 2021, at 15:00 +0600 and will run for 4 hours.

The contest will take place at Toph.co

This is not a rated contest. You can register for the contest here.

Problems of this contest were prepared and tested by Hasinur_, Shefin_, Joty TarifEzaz and me.

Thanks to TarifEzaz for his unconditional support and hjr265 for the best contest programming platform in Bangladesh.

We're inviting you all to participate in this contest. Hope you will enjoy the problem set.
There will be an editorial for this contest shortly after the round ends.

Contest Link: Replay of PIHACKS'21-CodeJam

Happy Coding!

Hello, Codeforces community!
I'm glad to invite you to Criterion 2021 Round 12 which will be held on April 09, 2021, at 16:00 +0600 and will run for 2 hours 30 minutes.

The contest will take place at Toph.co

This contest is rated for all participants. You can register for the contest here.

Problems of this contest were prepared and tested by upobir, Anachor, jAckAL_1586, Hasinur_, ishtupeed, TarifEzaz and me.

Thanks to TarifEzaz for his unconditional support and hjr265 for the best contest programming platform in Bangladesh.

We're inviting you all to participate in this contest. Hope you will enjoy the problem set.
There will be an editorial for this contest shortly after the round ends.
Feel free to share your experience with previous Criterion Rounds!

Contest Link: Criterion 2021 Round 12

Happy Coding!

Hello, Codeforces community!
I'm glad to invite you to Criterion 2021 Round 11 which will be held on March 19, 2021 at 16:00 +0600 and will run for 2 hours 30 minutes.

The contest will take place at Toph.co

This contest is rated for all participants. You can register for the contest here.

Problems of this contest were prepared and tested by upobir, Shefin_, Hasinur_, TarifEzaz and me.

Thanks to TarifEzaz for his unconditional support and hjr265 for the best contest programming platform in Bangladesh.

We're inviting you all to participate in this contest. Hope you will enjoy the problem set.
There will be an editorial for this contest shortly after the round ends.
Feel free to share your experience with previous Criterion Rounds!

Contest Link: Criterion 2021 Round 11

Happy Coding!

Hello, Codeforces community!
I'm glad to invite you to Criterion 2021 Round 10 which will be held on February 26, 2021 at 16:00 PM +0600 and will run for 2 hours 30 minutes.

The contest will take place at Toph.co

This contest is rated for all participants. You can register for the contest here.

Problems of this contest were prepared and tested by Shefin_, Hasinur_, TarifEzaz and me.

Thanks to TarifEzaz for his unconditional support and hjr265 for the best contest programming platform in Bangladesh.

We're inviting you all to participate in this contest. Hope you will enjoy the problem set.
There will be an editorial for this contest shortly after the round ends.
Feel free to share your experience with previous Criterion Rounds!

Contest Link: Criterion 2021 Round 10

Happy Coding!

Update: Editorials are out and problems are open for submissions!

Hello, Codeforces community!
I'm glad to invite you to Criterion 2021 Round 9 which will be held on February 5, 2021 at 16:00 PM +0600 and will run for 2 hours 30 minutes.

The contest will take place at Toph.co

This contest is rated for all participants. You can register for the contest here.

Problems of this contest were prepared and tested by ovis96, jAckAL_1586, Hasinur_, TarifEzaz, oasiscse and me.

Thanks to TarifEzaz for his unconditional support and hjr265 for the best contest programming platform in Bangladesh.

We're inviting you all to participate in this contest. Hope you will enjoy the problem set.
There will be an editorial for this contest shortly after the round ends.
Feel free to share your experience with previous Criterion Rounds!

Contest Link: Criterion 2021 Round 9

Happy Coding! UPD: Only 30 minutes to go!

Hello, Codeforces community!
I'm glad to invite you to Criterion 2021 Round 8 which will be held on January 15, 2021 at 15:00 PM +0600 and will run for 2 hours 30 minutes.

The contest will take place at Toph.co

This contest is rated for all participants. You can register for the contest here.

Problems of this contest were prepared and tested by upobir, jAckAL_1586, Hasinur_, ishtupeed, TarifEzaz and me.

Thanks to TarifEzaz for his unconditional support and hjr265 for the best contest programming platform in Bangladesh.

We're inviting you all to participate in this contest. Hope you will enjoy the problem set.
There will be an editorial for this contest shortly after the round ends.
Feel free to share your experience with previous Criterion Rounds!

Contest Link: Criterion 2021 Round 8

Happy Coding!

Any suggestions, please?

Hello, Codeforces community! I'm glad to invite you to — Replay of Intra UAP Programming Contest 2020, which will be held on Thursday, August 13, 2020, at 7:00 PM +0600 and will run for 3 hours.

The contest will take place at Toph.co

Since this is a replay contest, we request all contestants and everyone else who has seen the problems of preliminary to refrain from making the problem set public.

You'll be given 8 problems and 3 hours to solve them. There will be an interactive problem.

Problems of this contest were prepared and tested by rebornplusplus, Imran_Bin_Azad, ShockProof, labib, Rayhan, tufaan42, symonhasan, R_Hasan, and me.

This contest is formatted as per the official rules of ICPC Regional Programming Contests( See Details ).

You can use C++11 GCC 7.4, C++14 GCC 8.3, C++17 GCC 9.2, C11 GCC 9.2, Go 1.13, Java 1.8, Kotlin 1.1, Node.js 10.16, Perl 5.30, PHP 7.2, PyPy 7.1 (2.7), PyPy 7.1 (3.6), Python 2.7, Python 3.7, and Ruby 2.6 in this contest.

Contest Link: https://toph.co/c/intra-uap-2020-r

This contest will be beginner-friendly and Codeforces Div.2 participants may find the problem-set interesting.

Happy Coding!

I've started writing a new blog.
The First series of tutorial is about the Breadth-First Search algorithm.
There are 4 parts in this series.
I have discussed tutorial of breadth-first search and printing the shortest path between two nodes.
Bi-Coloring Problem.
Finding the shortest cycle of an unweighted graph.
2D-Grid bfs.
Multiple source bfs.
Passing flow through edges of bfs.
0-1 Breadth-First Search.
How to find the nodes lying in the all possible shortest path between two nodes.
And some other interesting applications of Breadth-First search.
Breadth-First Search. Part 1
Breadth-First Search. Part 2
Breadth-First Search. Part 3
Breadth-First Search. Part 4

I have written another blog about Prime numbers and prime checking.
Prime Numbers and Prime checking

Facebook Page of my blog.
All the article can be found in both English and Bangla.
Please let me know if there are any mistakes.
Finally sorry for my poor English.
Happy Coding.

I've been trying to solve one of my solved problem. 6151 — Beehives

I've sovled it a along time ago. It's giving me WA. Just a simple problem, finding the shortest cycle. Then I submitted my previous Accepted code. But it also giving me Wrong Answer verdict.

Here is my previous accepted code. Now I am afraid to try and solve another problem on that judge. Is there any issues?

Thank You.

Anyone who is unregistered, it's showing remaining time of the contest is 11 hours and 43 minutes. But after the registration it's showing 2 days remaining. Link to screenshot screenshot feature is not working for me. Don't no why.

UPD: Seems like fixed now.

Hello, Codeforces community! I'm glad to invite you to — Replay of Ada Lovelace National Girls' Programming Contest 2020 Preliminary, which will be held on Monday, December 23, 2019 at 7:00 PM +0600 and will run for 5 hours.

The contest will take place at Toph.co.

Since this is a replay contest, we request all contestants and everyone else who has seen the problems of preliminary to refrain from making the problem set public.

You'll be given 11 problems and 5 hours to solve them.

Problems of this contest were prepared and tested by CLown1331, Dhruba10414, 0pangktey0, fsshakkhor, Hasinur_, shadowfax, mahbubcseju, Moshiur_, rebornplusplus, Hasnaine_, I_Love_Light, BumbleBee, tanus_era, TarifEzaz, TariqueNasrullah, I_love_ProParThinkNot and me.

This contest is formatted as per the official rules of ICPC Regional Programming Contests( See Details ). You can use C++11 GCC 7.4, C++14 GCC 8.3, C++17 GCC 9.2, C11 GCC 9.2, Java 1.8, Python 2.7, and Python 3.7 in this contest.

This is the Contest Link

Happy Coding!

Hello, Codeforces community! I'm glad to invite you to Replay of VU CSE Tech Fest 2019 Programming Contest, which will be held on saturday, December 21, 2019 at 7:30 PM +0600 and will run for 5 hours.

The contest will take place at Toph.co

Since this is a replay contest, we request all contestants and everyone else who has seen the problems onsite to refrain from making the problem set public.

You'll be given 11 problems and 5 hours to solve them.

Problems of this contest were prepared and tested by TarifEzaz, fsshakkhor, fire_tornado, shadowfax, ishtupeed, De.Wilde, nahidhasan98, shahed_ahmed, Joty, BumbleBee, tahmedge, I_love_ProParThinkNot and me.

This contest is formatted as per the official rules of ICPC Regional Programming Contests( See Details ). You can use C++11 GCC 7.4, C++14 GCC 8.3, C++17 GCC 9.2, C11 GCC 9.2, Java 1.8, Python 2.7, and Python 3.7 in this contest.

This is the Contest Link

Happy Coding!

Orlin's algorithm has a complexity of O(n*m). It's the fastest. Why most of the programmers uses Dinic's algorithm or Edmond-Carp algorithm instead of Orlin's algorithm?

Though, I don't know anything about Orlin's algorithm.

Orlin's algorithm

I've learned Heavy light decomposition and found This Problem on Anudeep's blog. I couldn't come up any idea how to solve this problem.

Given a undirected weighted tree with N nodes ( N <= 1e5 )

All the nodes are white initially.

And Q queries ( Q <= 1e5 )

Update — Change the color of given node ( Black to White or White to Black )

Query — If there are at least one node with white color, find the maximum distance between any two nodes ( a , b ). a == b can be allowed.

Cost of edges can be negative.

Thank You.

I've a fear of bracket sequence. Whenever I face one, It scares me. So, I'm gonna solve as many as possible. I was trying to make a list of problems which contains dealing with "Bracket Sequences". Here are some. Please suggest some if you've solved any. It'll be so kind if you comment the topic with the problem.

Thank You in advance.

Happy Coding O_o.

Reading Material CP-Algorithm

Online Judge — Parentheses Balance ( Stack )

Codechef — Convert the Expression ( Infix / Postfix / Prefix conversion )

Online Judge — Equation ( Infix / Postfix / Prefix conversion )

Codeforces — Sereja and Brackets (Segment Tree)

Online Judge — Balanced String ( Constructive Algorithm )

Codeforces — Bracket Subsequence

Codeforces — Bracket Subsequence

Kattis — Pieces of Parentheses

Codechef — Matched Brackets

Codeforces — Longest Regular Bracket Sequence

Codeforces — Correct Bracket Sequence Editor

Codeforces — Serval and Parenthesis Sequence

Codeforces — Streets of Working Lanterns — 2

usaco

Jeff and Brackets

Codeforces — Replace To Make Regular Bracket Sequence

[Codeforces — Compressed Bracket Sequence ] https://codeforces.me/problemset/problem/1556/C

[CodeChef: Zonal Computing Olympiad 2012 ] https://www.codechef.com/ZCOPRAC/problems/ZCO12001

I've a graph consisting of 22 nodes and 36 edges. It's an undirected graph. From each node, I've to find the number of ways that I can reach all other nodes. Any idea please?

I just learned Ford-Fulkerson Algorithm for Maximum Flow Problem with BFS/DFS. I solved one problem from lightoj.com.

But I couldn't find any basic problem to practice the basic algorithm.

If someone can provide me some very basic problem, by practicing them I'll get used to the basic concept & coding also learn something I'll be really very grateful. I've some problems but those are not basic.

Thank You.

I was trying to solve this problem. With this code I got several WA & wasted hours of time by debugging it. But I've changed to this got AC! With no change of idea. All I changed was a line of code O_o.

it = lower_bound( v.begin() , v.end() , com [ i ].size() );

to

a = com [ i ].size();

it = lower_bound( v.begin() , v.end() , a );

Is there any problem with that?

Thank You.

In this problem I used set < pair < int , int > > st;

auto it = lower_bound( st.begin(), st.end(), make_pair( a + d + 1 , 0 ) )

But it costs me several TLE. But when I look over the tutorial solution, I saw this-

it = st.lower_bound( make_pair( a + d + 1 , 0 ) );

I used it, & got AC.

But I don't understand what's the difference? If anyone can please help. TLE Submission AC Submission Thank You O_o