what's wrong with the queue, 20mins have passed and my code is still in queue?

There was no contests today and no rejudging, so why so long queues

Before contest

Codeforces Round sponsored by NEAR (Div. 1 + Div. 2)

26:03:39

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Codeforces Round sponsored by NEAR (Div. 1 + Div. 2)

26:03:39

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*has extra registration

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Hello, following my previous blog, I'm adding the new problems I found interesting/teaching, so let's get into the problems

Note: these problems are mostly for the range of [pupil, expert] level, an average specialist with a bit of sweat will be able to solve them all

1549C - Web of Lies

553A - Kyoya and Colored Balls

333D - Characteristics of Rectangles

1873E - Building an Aquarium

1873H - Mad City

363D - Renting Bikes

358D - Dima and Hares

1624D - Palindromes Coloring

1928C - Physical Education Lesson

1918E - ace5 and Task Order

1834D - Survey in Class

1931F - Chat Screenshots

1931D - Divisible Pairs

1931G - One-Dimensional Puzzle

343C - Read Time

551C - GukiZ hates Boxes

1904D1 - Set To Max (Easy Version)

1904D2 - Set To Max (Hard Version)

1705D - Mark and Lightbulbs

1930C - Lexicographically Largest

1930D1 - Sum over all Substrings (Easy Version)

1930D2 - Sum over all Substrings (Hard Version)

1932C - LR-remainders

1926G - Vlad and Trouble at MIT

20A - BerOS file system

782B - The Meeting Place Cannot Be Changed

573B - Bear and Blocks

965D - Single-use Stones

1629D - Peculiar Movie Preferences

1923C - Find B

1251D - Salary Changing

1923D - Slimes

378C - Maze

1933E - Turtle vs. Rabbit Race: Optimal Trainings

1930E - 2..3...4.... Wonderful! Wonderful!

1272D - Remove One Element

1909B - Make Almost Equal With Mod

1909C - Heavy Intervals

1909D - Split Plus K

1909F1 - Small Permutation Problem (Easy Version)

480C - Riding in a Lift

380C - Sereja and Brackets

1365D - Solve The Maze

607B - Zuma

1941G - Rudolf and Subway

1077D - Cutting Out

1610C - Keshi Is Throwing a Party

1856C - To Become Max

1862F - Magic Will Save the World

1948D - Tandem Repeats?

1462E1 - Close Tuples (easy version)

1462E2 - Close Tuples (hard version)

237C - Primes on Interval

231C - To Add or Not to Add

1061C - Multiplicity

1486C1 - Guessing the Greatest (easy version)

1486C2 - Guessing the Greatest (hard version)

1569D - Inconvenient Pairs

The problems aren't in any specific order but higher problems may be a bit easier

These problems' requirements are intermediate dp, binary search, pure logic, algorithmic thinking, and math.

and I've solved all of them so feel free to check my submissions if u wanted

As we all have noticed it's been a while that tourist wasn't doing as well as before in the contests and had dropped to the rank 13, but yesterday he crushed the Div1 solving to E2 and got the rating change of +125.

When I started cp he was the first in cf, and seeing him dropped was a weird thing, tourist the legend of legends dropped to 13th, but he proved us again that is the best by re-getting first.

Congratulations

Hello cf community, in this blog I tried to gather binary search problems that are worth solving and maybe makes you learn it better, if there exist any blog tell me I'll remove this

1486D - Максимальная медиана

1486C1 - Найти наибольшее (простая версия)

1486C2 - Найти наибольшее (сложная версия)

883I - Photo Processing

1707A - Дореми и её IQ

1945E - Бинарный поиск

1623C - Сбалансированные кучки камней

1117C - Волшебный корабль

1862F - Волшебство спасёт мир

1856C - Стать максимумом

1610C - Кеши устраивает вечеринку

1077D - Вырезание массива

1730B - Собрание на прямой

1622C - Присвоить или уменьшить(doesn't need binary search)

1073C - Вася и робот

1923D - Слизни

782B - Место встречи изменить нельзя(recommended to solve)

343C - Время чтения

551C - GukiZ ненавидит коробки

1698D - Угадывание неподвижной точки

333D - Характеристики прямоугольников

1902D - Запросы робота(not binary search focused, just a tool)

1853C - Набор Ntarsis

1843E - Слежка за отрезками

251A - Точки на прямой

371C - Гамбургеры

372A - Весело считать Кенгуру

460C - Подарок

448D - Про таблицу умножения

670D2 - Волшебный порошок - 2(thanks to Arpa)

codechecf QHOUSE (also thanks to arpa)

1520F1 - Угадай K-й ноль (простая версия)

1520F2 - Угадай K-й ноль (сложная версия)

These problems are mostly specialist/expert level based but everyone can solve them, have fun and Hope you enjoy them

Peace

In a weird high school, there are $$$n$$$ students, and the school principal Mr. X wants to make students happy so he decides to throw a couples' party.

In this high school, between every 2 person, there can be 4 types of relationships:

1: they love each other

2: The first loves the second but the second doesn't

3: The second loves the first but the first doesn't

4: they don't like each other

At this party, people will be grouped into Pairs of couples.

The relationship between them determines the happiness of a pair:

type 1: happiness 2, type 2,3: happiness 1, type 4: happiness -1

if a person gets left out(I.E n is odd) there will be a -2 happiness for him

Since Mr. X is a happy person he wants to maximize the sum happiness of the party. Since he is a busy person He asks you to do that

**Input Format**

In The First Line, there will be one integer $$$n$$$: $$$n$$$, ($$$1 \leq n \leq 10^5$$$) the number of people at the party. In the Second line will be $$$m$$$, the number of people who love a person ($$$1 \leq r \leq 10^5$$$)

In the following $$$m$$$ lines there will be a format: two indexes $$$i$$$, $$$j$$$ meaning the person $$$i$$$ loves the person $$$j$$$. (Two-sided love will be given in 2 separate lines, if there isn't a directed edge between 2 people their relationship is type 4)

**Output Format** In the only line of the output, print the maximum happiness of the party

So today I came up with this problem and actually got stuck in solving it. Appreciate any helps

Hello, In this blog, I've tried to share my opinion on how to get good at dp problems, so stick to the end

in my opinion, dp is 85% thinking on paper, 10% thinking in your brain and 5% implementation.

so if you approach a dp problem always have pencil and paper and ** USE THEM** another thing is just solving the DP problems in combinatorics.

What do I mean?

**Question. 1** Given $$$n$$$, generate the set $$$s$$$ s.t $$$s = {1, 2, 3, 4, ..., n-1, n}$$$ then

count the number of subsets, where those elements in the set have *at least 1 element in between them*;

for example, $$$n = 8$$$ then $$$s = {1,2,3,4,5,6,7,8}$$$, one valid subset would be $$${1,4,8}$$$.

let $$$f_n$$$ be the solution of $$$n$$$, now let's backtrace,

$$$n$$$ comes -> $$$n-1$$$ won't come, but $$$n-2$$$ can be in the subset, but necessarily isn't so $$$f_{n-2}$$$

$$$n$$$ doesn't come -> $$$n-1$$$ can be so $$$f_{n-1}$$$

giving us $$$f_n = f_{n-1} + f_{n-2}$$$

**Question. 2** Same as *Question 1* but should have *at least 2 elements in between them*

let $$$f_n$$$ be the solution of $$$n$$$, now let's backtrace,

$$$n$$$ comes -> $$$n-1$$$ won't come, neither $$$n-2$$$ will, but $$$n-3$$$ can be in the subset, but necessarily isn't so $$$f_{n-3}$$$

$$$n$$$ doesn't come -> $$$n-1$$$ can be so $$$f_{n-1}$$$

giving us $$$f_n = f_{n-1} + f_{n-3}$$$

**Question. 3** Same as *Question 1*, Let's stop it

Let $$$a_n$$$ be the number of binary strings with *ab*, s. t no three consecutive characters are *a*.

find a recursive formula for $$$a_n$$$.

So the current string with length $$$n$$$ either was another string with length $$$n-1$$$ with the *b* at the end,

or was $$$n-2$$$ with *ba* at the end or $$$n-3$$$ with *baa* at the end. So $$$a_n = a_{n-1} + a_{n-2} + a_{n-3}$$$

Since the problems I've are in Persian and translating them would be a pain, Message me and I'll send them to you if you want but the translation is on you

Hope this Helped

Hello, CF community, I found this 1700*-ish problem, can somebody help?

Given $$$n$$$, $$$d$$$ positive integers, and the array $$$a$$$ with length $$$n$$$

for each $$$i$$$ s. t $$$1 \leq i \leq n$$$

Find the maximum j s. t $$$\vert{a_i - a_j}\vert \leq d$$$

**Input format:**

Integers n,d: $$$1 \leq n \leq 1e5, 1 \leq d \leq 1e9$$$

In the next line given $$$n$$$ integers representing $$$a_1$$$, $$$a_2$$$, ..., $$$a_{n-1}$$$, $$$a_n$$$

**Output format:**

In single line for each $$$1 \leq i \leq n$$$ output the corresponding $$$j$$$

if there is no corresponding $$$j$$$ output -1

I'd appreciate a solution without any kind of advanced data structure(___Trees, ___Arrays, etc)

Thanks for any help

Hello CF community, in this blog post I tried to gather the Questions I've solved and enjoyed them most of them are really teaching and worth spending hours of time on them Hope you enjoy

**EDIT: Part 2 added, link**

1418C - Mortal Kombat Tower

1311D - Three Integers

474D - Flowers

343C - Read Time

1918D - Blocking Elements

515C - Drazil and Factorial

1156C - Match Points

1853C - Ntarsis' Set

1843E - Tracking Segments

1843F1 - Omsk Metro (simple version)

1884D - Counting Rhyme

1884C - Medium Design

372A - Counting Kangaroos is Fun

455A - Boredom

1886D - Monocarp and the Set

1624D - Palindromes Coloring

448D - Multiplication Table

1092D1 - Great Vova Wall (Version 1)

479E - Riding in a Lift

1907E - Good Triples

1520F1 - Guess the K-th Zero (Easy version)

1520F2 - Guess the K-th Zero (Hard version)

1201C - Maximum Median

1374D - Zero Remainder Array

1922D - Berserk Monsters

1705C - Mark and His Unfinished Essay

380A - Sereja and Prefixes

747F - Igor and Interesting Numbers

1920D - Array Repetition

1920C - Partitioning the Array

831C - Jury Marks

1398C - Good Subarrays

1000C - Covered Points Count

1526C2 - Potions (Hard Version)

368B - Sereja and Suffixes

1324D - Pair of Topics

520B - Two Buttons

1901D - Yet Another Monster Fight

1919C - Grouping Increases

1574C - Slay the Dragon

1076C - Meme Problem

1349A - Orac and LCM

1358C - Celex Update

1458A - Row GCD

1539D - PriceFixed

1537E1 - Erase and Extend (Easy Version)

1497C2 - k-LCM (hard version)

1285C - Fadi and LCM

Note that to solve these problems you need no knowledge except:

9th grade math, a little bit number theory, sorting, elementary dp, elementary bs, set, stack, queue, map

Good luck and hope you enjoy them

EDIT: I added maybe a few problems, I ran out of beautiful problems, unfortunately, maybe suggest in the comments and I'll add them

**Guys a question: do u want me to include recent contests as well?**

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