brain

後 (after, behind): 9 strokes, JLPT N5. On: ゴ、コウ. Kun: あと、うし-ろ、のち.

We are given a binary string consisting only of 'a' and 'b'. For every substring, we repeatedly merge consecutive equal characters into a single character.

HSK 3 | verb/noun | an upward rise in quantity or degree

HSK 3 | adjective / verb | clear, distinct; to be clear about something

海 (kai/umi): sea. JLPT N5 kanji.

HSK 2 | measure word/noun | used for floors of a building and layers of things

国 (koku/kuni): country. JLPT N5 kanji.

HSK 5 | verb/noun | to assess, evaluate, or appraise performance; an assessment

HSK 4 | verb | officially occupying a role or post

HSK 5 | n | a group of writers sharing common aesthetic principles or historical context

HSK 2 | verb/preposition | to use something, to employ, with/using (as a preposition)

Sindarin nominal suffixes for possession, diminution, and verbal nouns: -en (mine), -weg (creature), -el (feminine), and the -as abstract noun suffix.

HSK 5 | adjective | on the brink of danger or extinction; endangered

We are given several stacks of unit cubes, each stack having an initial height. In a single move, we can take exactly one cube from the top of one stack and place it on top of another stack.

Guidelines for composing grammatically correct Neo-Sindarin: the scholar's toolkit, morphotactic constraints, how to coin new words, and how to evaluate others' Neo-Sindarin.

HSK 3 | verb / noun | to choose, select; a choice or selection

HSK 5 | noun / adjective | peace; peaceful

We are given a directed graph where every edge has a weight. We want the longest possible path measured by the number of edges, with one restriction: whenever we move from one edge to the next, the new edge must have a strictly larger weight than the previous one.

三 (san/mit-tsu): three. JLPT N5 kanji.

HSK 5 | verb/noun | to have an effect on someone or something; the effect produced

Learn 〜こそ and 〜だからこそ to place emphatic focus on a specific element — 'it is precisely X' and 'precisely because of X.'

HSK 5 | noun/adjective | health; healthy; sound; well

Learn 〜わけがない (there's no way ~, it's impossible that ~) — the N3 pattern for expressing strong logical impossibility based on the speaker's conviction.

Esperanto vocabulary for foods, drinks, cooking, meals, and restaurant situations.

The problem gives you the first n positive integers, arranged as a sequence 1 through n. You are allowed to combine any two numbers from this sequence using addition, subtraction, or multiplication, replacing the pair with the result.

HSK 5 | noun | the substance or information contained within something

Master five N3 patterns for describing change, tendencies, and degrees of difficulty: 〜ようになる, 〜ようにする, 〜がちだ, 〜やすい/〜にくい, and 〜得る/〜得ない.

Master the spectrum of Japanese registers from casual speech to formal written language, including 書き言葉 vs 話し言葉, contractions, and formal sentence-ending patterns like 〜である.

N1 grammar pattern 〜ずにはおかない: expressing that something inevitably happens or that the speaker will certainly do something — 'cannot help but, will surely, is bound to.'

Complete HSK 5 vocabulary reference: approximately 1,600 new words at B2 level, organized by semantic category with pinyin, English, part of speech, and usage notes.

HSK 5 | verb / noun | to call on, to appeal to; a call, an appeal

中 (middle, inside): 4 strokes, JLPT N5. On: チュウ. Kun: なか.

HSK 3 | preposition | toward, in the direction of — indicates direction of movement

N1 grammar pattern 〜ことなく: literary 'without doing X' expressing complete, absolute non-occurrence of an action throughout a period. Higher register than 〜ずに or 〜ないで.

HSK 5 | phrase | a connector used to introduce additional points or items

HSK 4 | noun | method, way, manner, mode

HSK 5 | verb/noun | to break apart into separate pieces; division or schism

HSK 3 | measure word | a unit of time lasting sixty seconds

HSK 3 | verb | to thank, feel grateful toward someone; more formal than 谢谢

HSK 5 | adjective/verb/noun | abstract; not concrete; to make abstract

We have an elevator starting on the first floor. Every person is waiting on that floor and wants to reach a specific destination floor. The elevator can carry at most k people at once. Moving between floors costs time equal to the floor difference.

HSK 5 | noun/verb | arbitration; to arbitrate; to mediate a dispute

HSK 4 | noun / verb | statistics; to compile statistics

HSK 1 | particle | asks 'and what about...?' or softens a statement

HSK 3 | verb | to exceed, surpass, or go beyond a quantity, limit, or standard

HSK 5 | verb/noun | to plan and coordinate as a whole; overall planning

HSK 4 | noun | a person who buys goods or services

Sindarin words for time: days, seasons, months, years, and the Elvish calendar (Kings' Reckoning and the Stewards' Reckoning).

Japanese numbers 1–10,000+, ordinal numbers, and the counter system (hon, mai, hiki, satsu, hai, ko, nin, and more) with examples.

Learn 〜だけでなく〜も (not only ~ but also ~) — the core N3 additive scope pattern for expanding beyond what was expected.

HSK 5 | noun/adjective | the state of being equal, especially in rights and status

Learn 〜たところ to express the discovery of an unexpected result upon completing an action, used in formal reports and investigations.

聞 (bun/mon/ki-ku): hear. JLPT N5 kanji.

HSK 5 | verb | to bear; to endure; to withstand pressure, pain, or hardship

HSK 3 | verb / adjective | to have a headache; troublesome, annoying

HSK 4 | adjective | conforming to reason, fairness, or accepted principles

HSK 1 | conjunction | introduces a reason or cause, paired with 所以

Master the vocabulary and formal register of Chinese business culture, including negotiation, formal reception, and professional social interaction.

Master the structure and language conventions of Chinese academic essays, including argumentative thesis writing, paragraph development, and formal transitions.

HSK 4 | adjective | showing energy, initiative, and a constructive attitude

HSK 6 | verb | to avoid or circumvent risks, rules, or obligations strategically

Express concession and unconditional assertions using 即使...也, 不管...都, 尽管...还是, and related patterns at B1 level.

HSK 3 | noun | shortcoming, weakness, flaw, disadvantage

Produce and evaluate scholarly work in Esperanto using correct academic register, citation practice, and the resources of the Esperanto research community.

HSK 2 | conjunction | presents alternatives in a statement; contrast with 还是 for questions

We are trying to win an election in a city with a known set of voters. Each voter currently supports a candidate numbered from 0 upwards, and each has a cost to bribe them to vote for you. Candidate 0 is ourselves.

HSK 5 | verb/noun | to return to health after illness or injury; the process of recovery

HSK 5 | verb/adjective | to streamline, trim, reduce to essentials; concise

HSK 1 | noun / measure word | mouth, opening, bite-sized portions

HSK 1 | noun | window

HSK 2 | adjective | easy to do, likely to happen

HSK 5 | adjective / adverb | existing or occurring generally among all people or in most places

HSK 5 | noun | channels of mass communication such as press, television, and the internet

HSK 4 | verb/noun | creating something new or improving existing things

HSK 5 | noun / verb | the point from which something originates; to originate from

HSK 4 | verb/noun | to grow or expand in a positive direction

HSK 3 | noun | the movement of vehicles and people; the transport system

出 (exit, appear): 5 strokes, JLPT N5. On: シュツ、スイ. Kun: で-る、だ-す.

HSK 6 | verb | to dissect and analyze in detail; to examine the inner workings of

HSK 5 | verb | to present; to emerge; to take on a certain appearance

HSK 4 | noun | a place where meals are served to customers

HSK 4 | verb / adjective | to understand; clear, obvious

HSK 5 | noun/verb | automation; to automate

HSK 3 | verb | to finish, accomplish, or fulfill a task or goal

HSK 4 | noun | a raw material or component used in cooking

Understanding 古今异义 and the semantic evolution of classical vocabulary in contemporary Chinese discourse.

HSK 3 | grammar pattern | passive sentence marking an action done to the subject, often with an unwanted result

HSK 5 | conjunction | even if, even though, no matter (strong concession)

HSK 3 | noun | spoken language, as opposed to written language

HSK 4 | verb | to initiate and carry out an activity or campaign

HSK 3 | noun | a section or component of a larger whole

HSK 5 | adjective/adverb | matching or responding appropriately to something

Japanese topic marker は (wa): marks the sentence topic, contrasts with が, usage in A-wa-B-desu patterns.

Learn 〜につれて (as ~ changes, proportionally) — expressing gradual co-change where two things change together.

JLPT N4 kanji 院 — readings, vocabulary, stroke order, mnemonic, and common confusion pairs.

HSK 5 | verb / adjective | to spread widely among the public; universally available or known

HSK 5 | noun | natural, human, or material resources available for use