brain

We are given a 4-digit lock. Each test case provides two states of this lock: a starting configuration and a target configuration. Each state consists of four digits in a fixed order, like a small array of length four.

We are given three input-output pairs of points on the extended complex plane, where each point is a complex number represented by its real and imaginary parts.

We start with a connected undirected graph where each edge has a weight. From this graph, we construct another graph called the line graph. In this transformed graph, every original edge becomes a vertex.

We are given a string of length $n$, where every character comes from a limited alphabet of size at most 20. From this string, we consider every nonempty subsequence.

We are given a string of length $n$, and we look at every non-empty prefix of this string. For each prefix, we apply a deterministic transformation that depends on the positions of characters inside that prefix. The transformation works as follows.

We are given a small grid maze with dimensions up to 100 by 100, and inside this grid there are exactly n adventurers and n escape ropes. Each adventurer starts at a unique cell, and each rope is also placed at a unique cell.

We are simulating a turn-based fight where a monster starts with a given amount of health, and each turn you receive exactly one random card. The card is uniformly chosen among three types.

We are given a sequence of circles placed one by one on a horizontal line. Each circle is fully determined by its center position on the x-axis and its radius, so every circle lies in the plane with center at $(xi, 0)$ and radius $ri$.

Let $q$ be a primitive $m$th root of unity and let $$N = n1 + cdots + nt.$$ Write each index in base $m$ form $$ni = m ai + ri,qquad 0 le ri < m,$$ and define $$A = a1 + cdots + at,qquad R = r1 + cdots + rt,$$ so that $N = mA + R$.

We are given a grid maze where some cells are walls and others are empty. A character starts from a fixed cell marked H at time zero and can move each minute to any of the four adjacent cells or stay in place. Movement is blocked by walls.

We are given an array and a fixed window size. In one move, we choose a contiguous segment of exactly length k and overwrite every element in that segment with the minimum value currently inside that segment.

Let $q$ be a primitive $m$th root of unity and let $$N = n1 + cdots + nt.$$ Write each index in base $m$ form $$ni = m ai + ri,qquad 0 le ri < m,$$ and define $$A = a1 + cdots + at,qquad R = r1 + cdots + rt,$$ so that $N = mA + R$.

We are given two independent groups of athletes, one group for sport A and one group for sport B. Each athlete has a numerical skill value, and every athlete must stay in their own sport unless we explicitly decide to “swap” them, meaning they compete in the other sport…

The problem statement is missing, so there’s no way to reconstruct the actual task, constraints, or required algorithm.

Let $q$ be a primitive $m$th root of unity and let $$N = n1 + cdots + nt.$$ Write each index in base $m$ form $$ni = m ai + ri,qquad 0 le ri < m,$$ and define $$A = a1 + cdots + at,qquad R = r1 + cdots + rt,$$ so that $N = mA + R$.

The problem statement for Codeforces 103428L - shake hands is missing in your prompt (it’s empty after “Problem Statement / Input / Output”).

I’m missing the actual problem content. Right now the prompt only contains the header for Codeforces 103428K - Tiny Stars, but the statement, input format, output format, and constraints are empty.

We are dealing with a classical billiards dynamics setup, but restricted to a perfectly circular table. A ball starts on the boundary of the circle and is shot inward with a given direction, represented by an angle.

I can’t reliably write a correct editorial for this yet because the actual problem statement is missing. Right now we only know the title “Distance”, but nothing about what “distance” is defined on, what the input represents, or what needs to be computed.

I can write the full editorial, but I’m missing the actual problem content. The statement section you provided for “Codeforces 103428H - city safety” is empty, so there’s no definition of: what the graph/array/city structure is, what “safety” means, what operations…

The problem statement is missing from your prompt, so there is no way to reconstruct the correct solution or write a meaningful editorial.

We are given all integers from 0 up to N, and we need to choose exactly K distinct numbers from this range. For every chosen subset, we compute the XOR of all its elements, then look at the binary representation of that XOR value and count how many bits are set to 1.

The problem statement for Codeforces 103428E - CHASE! is missing from your prompt, so I don’t have the actual rules, inputs, or required output to base an editorial on.

Let $q$ be a primitive $m$th root of unity. For each $i$ with $1 le i le t$, write $$ni = m ai + bi, qquad 0 le bi < m,$$ and set $$N = n1 + cdots + nt, qquad A = a1 + cdots + at, qquad B = b1 + cdots + bt,$$ so that $N = mA + B$.

The problem statement section is empty, so there isn’t enough information to reconstruct what Codeforces 103428A - “Goodbye, Ziyin!” is asking. An editorial depends completely on the operations, constraints, and output definition.

Fix $n,t,r$.

A World Series scenario in the sense of exercise 10 is a sequence of games between $A$ and $N$ that stops when one side reaches four wins.

Let the canonical bases be represented in the form $(\alpha_1,\dots,\alpha_t)$ as in exercise 12, where each $\alpha_i$ is a binary string of length $n$ with exactly one distinguished position equal t...

We are given a fixed string consisting of lowercase letters. Then we receive many queries; each query temporarily changes one position of the string into a special character , and we must answer a question about the modified string.

Let $G$ be the multigraph whose vertices are ${0,1,2,3,4,5,6}$ and whose edges are the $28$ dominoes of the double-six set, namely one edge between $i$ and $j$ for each $0 \le i \le j \le 6$, includin...

Let $G$ be the multigraph whose vertices are ${0,1,2,3,4,5,6}$ and whose edges are the $28$ dominoes of the double-six set, namely one edge between $i$ and $j$ for each $0 \le i \le j \le 6$, includin...

Let $G_{s,t}$ denote the graph whose vertices are all subcubes of length $s+t$ having $s$ digits in ${0,1}$ and $t$ asterisks, with edges given by the transformations $\ast 0 \leftrightarrow 0\ast$, $...

Let the universal cycle be $a_0,a_1,\dots,a_{L-1}$, indexed cyclically modulo $L$, over the alphabet ${0,1,\dots,n-1}$.

Let $n=s+t$ and let the ground positions be ${0,1,\dots,n-1}$.

Let $n=s+t$ and let the ground positions be ${0,1,\dots,n-1}$.

We are given three separate text lines, and each line must be checked against a target vowel count pattern. The pattern is fixed as 5 vowels in the first line, 7 vowels in the second line, and 5 vowels in the third line.

We are given two points on a 2D grid, call them A and B. Each point has integer coordinates, and distances are measured in the standard geometric sense.

We are given a sequence of locations arranged in a line. Each location initially contains some amount of trash. There is a cleaning process that involves choosing a number of workers, and these workers move through the locations in order, cleaning trash at each one.

Let $I \subseteq \mathbb{C}[x_1,\dots,x_s]$ be a homogeneous polynomial ideal.

We are given a system of positions indexed from 1 to n. Each position has a rule that determines where we move next: from i we either move one step forward to i + 1, or we make a larger jump to i + k[i]. Which of the two happens depends on a changing parameter x.

The problem describes a system where a player starts with an initial rating and plays a sequence of matches. Each match is not just a simple increment or decrement, but depends on a chosen “opening” that affects how the rating evolves across subsequent games.

We are effectively navigating a grid of states, where each state represents owning a particular armor type and a particular weapon type.

We are given a collection of segments, each segment representing a Tetris piece placed on a row. Each piece occupies a continuous interval on a number line, from a left endpoint $Li$ to a right endpoint $Ri$, and carries a value $ci$.

We are given a set of students. Each student is associated with a specific message index and a limit value that controls how reliably they will read a pinned message depending on how many total messages are pinned.

The process in this problem is easiest to think of as a sequence that grows step by step, where each step corresponds to sending one more message in a chat, and each message contributes a certain number of “emotes” depending on its position in the sequence.

We are given a pair of positive integers, and we repeatedly apply an operation that always acts on the larger value. The only move allowed is to replace the larger number by its difference with the smaller one. The process continues until one of the numbers becomes zero.

We are given an array where each value can be thought of as a type, and each type has a frequency. The task is to construct a permutation of the array that maximizes a certain global score that depends on how many times equal values interact across positions.

We are working with a permutation construction problem where two special values, say a and b, define a directional constraint over positions.

I don’t have the actual problem statement for Codeforces 103433J - Two Prefixes in your message, so I can’t reliably reconstruct the task or derive a correct solution without risking inventing details.

I can’t write a correct, faithful editorial for this yet because the problem statement is missing. Right now I only see the title “The Pleasant Walk”, but no description of what the input represents, what operation is being performed, or what needs to be computed.

Let $(a_{ij})$ be an $m\times n$ contingency table with nonnegative integer entries, row sums $r_i=\sum_{j=1}^n a_{ij},$ and column sums $c_j=\sum_{i=1}^m a_{ij},$ with $\sum_{i=1}^m r_i=\sum_{j=1}^n...

I can’t reliably produce a correct, problem-specific editorial yet because the actual statement for Codeforces 103433L - Berland University is not available from the sources I can see, and this problem ID appears to be an unrated / less-indexed contest task where the…

I can’t reliably write a correct editorial for Codeforces 103433K - Right Expansion Of The Mind because the actual problem statement (input/output rules, constraints, and operations) is missing.

We are given a line of food stops placed along a one-dimensional road. Each stop has a fixed position to the right of the starting point and a fixed amount of time required to consume it.

I don’t have the actual statement of Codeforces 103433I - Minimal Product available in your prompt, and I can’t reconstruct a correct editorial without knowing what the input/output and constraints are.

I don’t have the problem statement for Codeforces 103433A - “Company Merging” in your message, and I can’t reliably reconstruct it from the ID alone without risking writing the wrong solution.

I’m missing the actual content of Codeforces 103433H - Linearization (the statement, constraints, and samples). Right now the “Problem Statement / Input / Output” sections are empty, so there’s nothing concrete to base the editorial on.

I can’t reliably write a correct editorial for Codeforces 103433G - Combostone because the actual problem statement is missing from your prompt.

I can’t write a correct editorial yet because the actual problem statement for CF 103433F - How to Learn You Score is missing from your prompt (both the “Problem Statement / Input / Output” sections are empty).

We are given an array and we are asked to decide a notion of similarity between arrays under a specific transformation rule.

I can write that editorial in the exact format you want, but I’m missing the actual problem statement for Codeforces 103433B - LaTeX Expert. Without the statement, any “solution” would be guesswork, and that would almost certainly produce a wrong editorial.

We are given a string made of digits 0, 2, 5, and 6, and we are allowed to change any character into any other allowed digit in a single operation.

We are given a hierarchy of paper sizes from $A0$ down to $AN$, where each level is exactly half the size of the previous one. You start with some initial inventory of sheets at each size, and you also have a target inventory you want to achieve.

We are asked to count special arrays of positive integers where multiplication and addition give the same result. For an array of length $k$, if the product of all elements equals the sum of all elements, we call it valid.

Let $(a_{ij})$ be an $m\times n$ contingency table with nonnegative integer entries, row sums $r_i=\sum_{j=1}^n a_{ij},$ and column sums $c_j=\sum_{i=1}^m a_{ij},$ with $\sum_{i=1}^m r_i=\sum_{j=1}^n...

Working

The game runs for a fixed number of rounds, and in each round the boss and the player interact through a shared system of stacking effects.

We are given a tree, and we are allowed to run a depth-first search that produces a post-order sequence: a node is written to the output only after all of its unvisited neighbors have been recursively processed. The twist is that we are not constrained to a fixed DFS behavior.

We are given a string of length $2n$, consisting only of the letters A, B, and C. The task is to split the set of positions of this string into $n$ disjoint pairs.

We are given two binary grids of the same size. Each cell is either 0 or 1, representing white or black. We start from grid A and are allowed to apply an operation that picks any cell, takes the entire connected region of equal-valued cells containing it, and flips every value…

We are given a permutation of size $n$, but the positions of this permutation are grouped by colors. We are allowed to fix the permutation using two kinds of actions: we can swap any two elements paying a fixed cost $S$, and we can also pick a color class and arbitrarily…

We are given a collection of 2n objects, each object i described by two integers ai and bi. You can think of each object as a segment on the number line, although the endpoints are not guaranteed to be ordered.

We are given an array that we are not allowed to reorder and a second set of spare numbers that can be used as replacements.

We are asked to construct two binary strings, call them S and T, with lengths up to a fixed limit. The goal is not to optimize a standard objective like LCS length itself, but to control the structure of the set of all longest common subsequences.

We are given two strings of equal length, say s and t, both indexed from 1 to n. For every substring that starts at position l and ends at position r, we compare the substring s[l..r] with t[l..r] using standard lexicographic ordering.

We are given a matrix with at most four rows and up to a quarter million columns. From each column we derive a single value by summing all rows in that column. So every version of the matrix corresponds to a one-dimensional array derived from column-wise sums.

We are working with a tree where each node has a color label. The task is to look at every connected set of nodes inside this tree, meaning any subset of vertices whose induced subgraph stays connected, and decide whether that set has a “majority color”.

An $(s,t)$-combination in dual form is a strictly decreasing sequence $b_s > b_{s-1} > \cdots > b_1 \ge 0,$ where ${b_1,\dots,b_s}$ are exactly the positions of the $0$’s in a binary string of length...

I can write the full editorial in exactly that format, but I’m missing the actual problem statement for Codeforces 103439M - Many LCS.

I’m missing the actual problem statement for Codeforces 103439N - Max Pair Matching (your prompt shows the section empty), so I can’t safely reconstruct the intended solution.

I don’t have the actual statement for Codeforces 103439K - Amazing Tree in your prompt, and the “Problem Statement” section is empty.

I don’t have the actual statement for Codeforces 103439L (“Primes and XOR? Nonsense”) in the prompt, and the task explicitly requires restating the problem, deriving constraints, and building correctness arguments from it.

I can’t reliably write a correct editorial for “Codeforces 103439J - Jason ABC” because I don’t have the problem statement, and I don’t want to invent details and accidentally give you a wrong solution.

I can’t reliably write a correct editorial without the actual problem statement. Right now the prompt only includes the title, but the core of the task, what operations are allowed, what “colourful permutation sorting” means in this context, and what constraints drive…

Let the given bit string be $a{25}dots a0$, where $s=12$ zeros and $t=14$ ones. In Chase’s sequence $C{st}$ as defined in (41), successive combinations are obtained by exchanging an adjacent pattern $10 leftrightarrow 01$, so a single move swaps a $1$ with a neighboring $0$.

We are given an array $A$ that we want to transform into a nondecreasing sequence. Alongside it, we have a separate set $B$ of spare values. Every element across $A$ and $B$ is distinct.

I can’t write a correct editorial for this yet because the actual problem statement is missing. “Codeforces 103439H - Werewolves” alone isn’t enough to reliably reconstruct the task.

I can’t reliably write a correct editorial for this because the actual problem statement is missing from your prompt. Right now I only have the title “103439F - to Pay Respects”, but no description of: - what the structure is (array, tree, graph, etc.

I can write a full editorial in the requested style, but I’m missing the most important piece: the actual problem statement for Codeforces 103439D - LIS Counting is not included in your prompt.

I can write the full editorial, but the problem statement section you provided is missing entirely (it’s blank). Without the actual rules of Codeforces 103439E - Flood Fill, I can’t accurately reconstruct the algorithm, examples, or edge cases without guessing.

An $(s,t)$-combination in dual form is a strictly decreasing sequence $b_s > b_{s-1} > \cdots > b_1 \ge 0,$ where ${b_1,\dots,b_s}$ are exactly the positions of the $0$’s in a binary string of length...

I can’t reliably write a correct editorial yet because the actual problem statement is missing from your prompt (the “Problem / Input / Output” sections are empty).

I can’t reliably write a correct editorial yet because the actual problem statement for Codeforces 103439A - ABC Legacy is missing from your prompt.

Let the given bit string be interpreted as an $(s,t)$-combination with $s=12$ zeros and $t=14$ ones, hence $n=s+t=26$. The string is $11001001000011111101101010.$ Chase’s sequence $C{st}$, as defined in equation (41), is a generating order on $(s,t)$-combinations.

The forest is represented as a small binary grid where each cell is either 0 or 1. A 1 means dense trees, a 0 means open bushes. The grid is surrounded by implicit zeros beyond its borders, so any step outside the matrix behaves like a 0 cell.

We are given two strings, a and b. The string a is inserted into every possible position of b, including before the first character and after the last one. If b has length m, this produces m + 1 different strings, each corresponding to a cut position in b.

We are given a complete graph where every pair of vertices is connected, but edge costs are not uniform. One special vertex acts as a warehouse (vertex 0), and every other vertex is either a “main street” store in set S or an “alley” store in set U.

Let the given bit string be interpreted as an $(s,t)$-combination with $s=12$ zeros and $t=14$ ones, hence $n=s+t=26$. The string is $11001001000011111101101010.$ Chase’s sequence $C{st}$, as defined in equation (41), is a generating order on $(s,t)$-combinations.

We are given a complete set of $2n$ people who must be paired into $n$ disjoint teams of size two. Between some pairs of people, a prior collaboration exists, and those pairs are considered “good” edges. Every other pair is “bad”.

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