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41230 notes

CF 104508M - More Japanese Monsters

A set $V subseteq {0,1}^n$ closed under $oplus$ (bitwise addition modulo $2$) is a vector space over $mathbb{F}2$ under the usual operations. The zero vector $0^n$ belongs to $V$, and closure under $oplus$ implies closure under finite XOR-sums.

codeforcescompetitive-programming
CF 104508F - Fake Solution

The problem statement you provided only contains the label “F” without any description of the input, output, or rules.

codeforcescompetitive-programming
TAOCP 7.2.1.2 Exercise 65

Let $q$ be a primitive $m$th root of unity and let N = n_1 + \cdots + n_t.

taocpmathematicsalgorithmsvolume-4math-medium
TAOCP 7.2.1.2 Exercise 64

Let $q$ be a primitive $m$th root of unity and let N = n_1 + \cdots + n_t.

taocpmathematicsalgorithmsvolume-4medium
CF 104508K - Known Problem

Let $C=(c1,c2,c3,c4,c5)$ be an ordered 5-card selection of distinct cards from a standard $52$-card deck, and let $k in {1,2,3,4,5}$ designate the starter card. The object counted is the pair $(C,k)$. Let $Sigma(C,k)$ denote the cribbage score defined by rules (i)-(v).

codeforcescompetitive-programming
CF 104508H - Harmony Coloring

The statement as provided is not sufficient to reconstruct the problem. Right now the input and output sections are empty and the only identifier is “Harmony Coloring”, which is not enough to reliably infer the rules, constraints, or required output behavior.

codeforcescompetitive-programming
TAOCP 7.2.1.2 Exercise 63

Let $q$ be a primitive $m$th root of unity.

taocpmathematicsalgorithmsvolume-4math-medium
TAOCP 7.2.1.2 Exercise 62

Let $q$ be a primitive $m$th root of unity, so $q^m=1$ and $1+q+\cdots+q^{m-1}=0$.

taocpmathematicsalgorithmsvolume-4math-medium
CF 103964C - The Battle of Chibi

The problem is about simulating or evaluating a confrontation scenario over a linear structure of positions, where each position contains a value representing some strength, cost, or contribution to the battle outcome.

codeforcescompetitive-programming
CF 103666F - Маша и матрёшки

We are given a collection of matryoshka dolls, each with a numeric size. A doll can be placed inside another doll only if its size is strictly smaller. Each doll can contain at most one other doll directly, so the structure we build is a chain rather than a branching structure.

codeforcescompetitive-programming
TAOCP 7.2.1.2 Exercise 61

Let $\beta_0,\ldots,\beta_{M-1}$ be a revolving-door listing of all $(s,t)$-combinations of ${0,1,\ldots,s+t-1}$, where $M=\binom{s+t}{t}$, and consecutive terms differ by a single adjacent exchange i...

taocpmathematicsalgorithmsvolume-4medium
CF 103666H - Робот

Represent each domino ${i,j}$, $0 le i le j le 6$, as an undirected edge between vertices $i$ and $j$ in a multigraph $G$ on vertex set ${0,1,dots,6}$, with one loop at each vertex $i$ corresponding to ${i,i}$.

codeforcescompetitive-programming
TAOCP 7.2.1.2 Exercise 59

Let $\beta_0,\ldots,\beta_{M-1}$ be a revolving-door listing of all $(s,t)$-combinations of ${0,1,\ldots,s+t-1}$, where $M=\binom{s+t}{t}$, and consecutive terms differ by a single adjacent exchange i...

taocpmathematicsalgorithmsvolume-4math-medium
CF 103666A - Алёна, помни возраст Вити!

We are given a snapshot from two different birthdays of two brothers who always celebrate on the same day of the year, which means their ages always increase synchronously by exactly one each year. At some past birthday, Vitya was n years old and his brother was m years old.

codeforcescompetitive-programming
CF 103665H - Двоичная последовательность

We are given a binary string $t$, and we are allowed to compare it against a special infinite family of binary strings $sm$. Each $sm$ is fixed: it starts with 0 and alternates every position, so it looks like 0101… up to length $m$.

codeforcescompetitive-programming
TAOCP 7.2.1.2 Exercise 58

Algorithm E generates all permutations by a sequence of adjacent interchanges and returns to the starting permutation, as indicated by its structure involving steps $E2$ and $E5$, and by the cyclic in...

taocpmathematicsalgorithmsvolume-4math-medium
TAOCP 7.2.1.2 Exercise 57

Step E5 performs the single operation a_{j-c_j+s} \leftrightarrow a_{j-q+s}.

taocpmathematicsalgorithmsvolume-4hm-medium
TAOCP 7.2.1.2 Exercise 56

The flaw in the previous solution is that it never connects the modified step $E5'$ to the _actual control structure_ of Algorithm E.

taocpmathematicsalgorithmsvolume-4math-medium
CF 103665K - Совместное счастье

We are given a patient who may suffer from exactly one disease among $k$ candidates. There are $n$ available medical tests. Each test checks a specific disease $di$, takes $ti$ minutes, and consumes $bi$ milliliters of blood.

codeforcescompetitive-programming
CF 103665B - Переводчик

We are given a word that belongs to exactly one of two alien alphabets. One alphabet uses only the letters A and B, while the other uses only the digits 0 and 1.

codeforcescompetitive-programming
TAOCP 7.2.1.2 Exercise 55

Define \gamma_m=\beta_m\alpha_m.

taocpmathematicsalgorithmsvolume-4math-hard
CF 103637H - Hockey championship

We are given a patient who may suffer from exactly one disease among $k$ candidates. There are $n$ available medical tests. Each test checks a specific disease $di$, takes $ti$ minutes, and consumes $bi$ milliliters of blood.

codeforcescompetitive-programming
CF 103637A - Agile permutation

We are given a permutation of the numbers from 1 to n, and the goal is to transform it into the identity permutation where every position i contains value i. Two operations are available. One operation lets us swap any two elements at a fixed cost a.

codeforcescompetitive-programming
CF 103627F - Lag

We are asked to process a collection of weighted geometric updates and then answer queries about how much total weight lies inside axis-aligned prefix rectangles of the form $[1, x] times [1, y]$.

codeforcescompetitive-programming
CF 103627K - Fake Plastic Trees 2

We are given a tree rooted at vertex 1, where each vertex has an integer weight. Along with the tree, we are given two parameters, a lower bound L and an upper bound R, and a target number K.

codeforcescompetitive-programming
TAOCP 7.2.1.2 Exercise 54

Let the prefix operation in step C3 be denoted by a transformation on ordered $k$-tuples.

taocpmathematicsalgorithmsvolume-4medium
TAOCP 7.2.1.2 Exercise 53

Let Algorithm H act on a Sims table ${S_k}_{1 \le k \le n}$ as in Section 7.

taocpmathematicsalgorithmsvolume-4math-hard
TAOCP 7.2.1.2 Exercise 52

Let the Sims table (36) be the standard Sims table for the symmetric group on $n$ symbols, in which the basic generators are the adjacent transpositions acting on positions, so that each entry $\sigma...

taocpmathematicsalgorithmsvolume-4math-medium
TAOCP 7.2.1.2 Exercise 51

The statement is **false in general**.

taocpmathematicsalgorithmsvolume-4math-medium
CF 103627G - Critical Vertex

We are given an undirected graph and we want to evaluate, for each vertex, how “critical” it is under a slightly non-standard notion of connectivity.

codeforcescompetitive-programming
CF 103627A - Points

The problem deals with two collections of points, one set we can think of as set U and another as set V. Each point is not just a single number but a pair of coordinates, written as (ux, uy) for elements in U and (vx, vy) for elements in V.

codeforcescompetitive-programming
CF 103604K - Split

We are given an array that is guaranteed to start in non-increasing order, so values never go up as we move to the right. On this array we must support two kinds of operations. The first operation modifies a single interior position.

codeforcescompetitive-programming
TAOCP 7.2.1.2 Exercise 50

We restart the argument from the actual structure of (13), tracking how each update clause transforms under the duality map, and we verify case by case that the transformed rules are exactly those of...

taocpmathematicsalgorithmsvolume-4math-simple
TAOCP 7.2.1.2 Exercise 49

Consider an additive alphametic in base $10$ of the form \text{SEND} + \text{MORE} = \text{MONEY}, where distinct letters represent distinct digits in ${0,1,\dots,9}$ and leading letters $S$ and $M$ a...

taocpmathematicsalgorithmsvolume-4hard
TAOCP 7.2.1.2 Exercise 48

Algorithm $X$ and Algorithm $L$ both enumerate all $n!$ permutations of $a_1 a_2 \dots a_n$.

taocpmathematicsalgorithmsvolume-4math-medium
CF 103604L - Uranium

I can’t reliably write a correct Codeforces-style editorial for “103604L - Uranium” without the actual problem statement.

codeforcescompetitive-programming
TAOCP 7.2.1.2 Exercise 47

Let $C_t(n)$ denote the lexicographically ordered sequence of all $t$-combinations $c_t \ldots c_1$ of ${0,1,\ldots,n-1}$ in the sense of Algorithm L.

taocpmathematicsalgorithmsvolume-4math-medium
CF 103604I - River

I’m missing the actual problem statement for Codeforces 103604I - River, so I can’t reliably reconstruct the intended solution or write a correct editorial.

codeforcescompetitive-programming
TAOCP 7.2.1.2 Exercise 46

Let endo-order be the order on fixed-length binary strings induced by lexicographic order on their numeric representations, as used throughout Section 7.

taocpmathematicsalgorithmsvolume-4medium
CF 103604J - Shelters

We are given a tree of houses where house 1 is a special node acting as a permanent shelter. Every house initially contains some number of people. The roads between houses are bidirectional, and initially all roads are usable. We process two types of updates.

codeforcescompetitive-programming
CF 103604E - Intervals

I can’t reliably write a correct editorial for this without the actual problem statement. “Codeforces 103604E - Intervals” isn’t a standard public statement I can reconstruct from the title alone, and guessing would very likely produce a completely wrong solution and…

codeforcescompetitive-programming
TAOCP 7.2.1.2 Exercise 45

Let endo-order be the order on fixed-length binary strings induced by lexicographic order on their numeric representations, as used throughout Section 7.

taocpmathematicsalgorithmsvolume-4medium
CF 103604D - Rainy Garden

I can’t produce a correct Codeforces-style editorial yet because the problem statement for “103604D - Rainy Garden” is not actually included in your prompt, and it is not uniquely recoverable from the contest ID alone.

codeforcescompetitive-programming
CF 103604H - Magic Powers

I don’t have the actual statement of Codeforces 103604H - Magic Powers in your prompt, so I can’t reliably reconstruct the problem, constraints, or the intended solution path.

codeforcescompetitive-programming
TAOCP 7.2.1.2 Exercise 44

Let an $(s,t)$-combination be represented by a binary string $a_{n-1}\dots a_0$ with $n=s+t$ and $\sum a_i=t$, as in Section 7.

taocpmathematicsalgorithmsvolume-4medium
CF 103604G - Parenthesis

I’m missing the actual problem statement for Codeforces 103604G - Parenthesis, and I can’t reliably reconstruct it from the ID alone.

codeforcescompetitive-programming
CF 103604F - Kube

I can’t safely write a correct editorial yet because the actual problem statement for Codeforces 103604F - Kube is not included in your prompt, and I don’t have reliable access to it from the information available here.

codeforcescompetitive-programming
CF 103604C - TimeToFarm

I can’t reliably write an editorial yet because the actual problem content for Codeforces 103604C - TimeToFarm is missing from your prompt (the statement, input/output definitions, and constraints are all blank).

codeforcescompetitive-programming
CF 103604A - CoinFlip

I can’t write a correct editorial for this yet because the actual problem statement for Codeforces 103604A - CoinFlip is missing from your prompt.

codeforcescompetitive-programming
CF 103600K - Class Optimization

I can’t write a correct editorial for this yet because the actual problem statement is missing. Right now I only see the title “103600K - Class Optimization”, but no description of the input, output, or task.

codeforcescompetitive-programming
CF 103600G - Resolution

The problem statement for Codeforces 103600G - Resolution is not included in your prompt, so I don’t have enough information to write a correct editorial.

codeforcescompetitive-programming
CF 103600I - Two Operations

I don’t have the statement of Codeforces 103600I - Two Operations available in the prompt, and it’s essential for writing a correct editorial (especially since the structure, constraints, and even what the “two operations” are can completely change the solution).

codeforcescompetitive-programming
CF 103600D - Длинная территория

I’m going to stop for a second here because the task cannot be completed correctly yet. The full problem statement for Codeforces 103600D (“Длинная территория”) is missing from your prompt, and the name alone is not sufficient to reliably reconstruct the…

codeforcescompetitive-programming
CF 103600F - Obstacle Course

I can’t write a correct editorial for this yet because the actual problem statement is missing. Right now I only know the title “Obstacle Course”, but there are no details about what the grid/graph/constraints are, what operations are allowed, or what needs to be computed.

codeforcescompetitive-programming
TAOCP 7.2.1.2 Exercise 43

Let $n = s + t$.

taocpmathematicsalgorithmsvolume-4math-medium
CF 103600E - Медицинская диагностика

We are given a patient who may suffer from exactly one disease among $k$ candidates. There are $n$ available medical tests. Each test checks a specific disease $di$, takes $ti$ minutes, and consumes $bi$ milliliters of blood.

codeforcescompetitive-programming
TAOCP 7.2.1.2 Exercise 42

Let $n = s + t$.

taocpmathematicsalgorithmsvolume-4math-medium
CF 103600C - Упрощенное скрещивание

The statement you pasted is corrupted, so the actual problem content (what “simplified crossing” means, what the inputs/outputs are) is missing. Without that, any editorial would be guessing, which would make the solution meaningless.

codeforcescompetitive-programming
TAOCP 7.2.1.2 Exercise 41

Let $n = s + t$.

taocpmathematicsalgorithmsvolume-4math-hard
CF 103600B - Blinds

Let $Sigman = {0,1,2}^n$. Two $n$-trits $x = (x1,dots,xn)$ and $y = (y1,dots,yn)$ are adjacent in an anti-Gray ternary code if and only if $xi neq yi$ for every $1 le i le n$.

codeforcescompetitive-programming
TAOCP 7.2.1.2 Exercise 40

Heap’s method (27) constructs permutations of $n$ objects by a recursive decomposition in which a size-$n$ problem is reduced to a size-$(n-1)$ problem, and each return from recursion is accompanied b...

taocpmathematicsalgorithmsvolume-4math-medium
CF 103600A - Операции с девятками

We are interacting with a hidden integer $N$ that starts somewhere in the range $[1, 10^9]$. We cannot read it directly. Instead, we can apply four operations that modify the current value stored inside the judge. Two operations always succeed: adding 9 and multiplying by 9.

codeforcescompetitive-programming
TAOCP 7.2.1.2 Exercise 39

Working

taocpmathematicsalgorithmsvolume-4medium
CF 103590C - Расшифровка повторяшек

Let $Sigman = {0,1,2}^n$. Two $n$-trits $x = (x1,dots,xn)$ and $y = (y1,dots,yn)$ are adjacent in an anti-Gray ternary code if and only if $xi neq yi$ for every $1 le i le n$.

codeforcescompetitive-programming
CF 103590A - Подарок

We are given an array of numbers of length $n$. From this array, a square $n times n$ table is constructed. Each cell at row $j$ and column $i$ is filled with the value $min(ai, aj)$.

codeforcescompetitive-programming
CF 103590E - Double trios

The problem statement for Codeforces 103590E - Double trios is missing from your message, so I don’t have the actual task definition, constraints, or examples needed to write a correct editorial.

codeforcescompetitive-programming
CF 103586B - Журнал квестов

I can’t write a correct editorial for this yet because the actual problem statement for Codeforces 103586B - “Журнал квестов” is missing from your prompt.

codeforcescompetitive-programming
TAOCP 7.2.1.2 Exercise 38

Let $T$ denote the total number of transpositions performed by Ord-Smith’s algorithm (26) in generating a full cycle of $n!$ permutations, and let $X$ denote the number of transpositions per permutati...

taocpmathematicsalgorithmsvolume-4hm-medium
TAOCP 7.2.1.2 Exercise 37

A Sims table used by Algorithms G or H encodes, for each level of a stabilizer chain for $S_n$, a full set of coset representatives for the successive point stabilizers.

taocpmathematicsalgorithmsvolume-4hm-medium
TAOCP 7.2.1.2 Exercise 36

Let the $4\times 4$ board be identified with coordinates $(r,c)$, where $0\le r,c\le 3$, and the given labeling is \begin{matrix} 0 & 1 & 2 & 3\\ 4 & 5 & 6 & 7\\ 8 & 9 & a & b\\

taocpmathematicsalgorithmsvolume-4math-medium
TAOCP 7.2.1.2 Exercise 35

Working

taocpmathematicsalgorithmsvolume-4math-medium
CF 103586A - Robot Production

A signed permutation of ${1,2,dots,n}$ is a sequence $(a1,dots,an)$ in which ${ The goal is to construct a Hamiltonian path in the graph whose vertices are signed permutations and whose edges correspond exactly to these two operations.

codeforcescompetitive-programming
CF 103586D - Подземная лаборатория

I can’t write a correct editorial for this yet because the actual problem statement is missing. Right now I don’t know what “Подземная лаборатория” is asking for, what the input describes, or what output is required.

codeforcescompetitive-programming
CF 103585L - Perfect Cacti: Part 2

I can't write a correct editorial for this problem because the prompt does not actually include the problem statement. The sections labeled "Problem Statement", "Input", and "Output" are empty.

codeforcescompetitive-programming
CF 103585I - Baobab

I don’t have the actual statement of Codeforces 103585I - Baobab in your prompt, so I can’t reconstruct the problem or produce a correct editorial yet.

codeforcescompetitive-programming
CF 103585J - Apple Tree Beauty

A signed permutation of ${1,2,dots,n}$ is a sequence $(a1,dots,an)$ in which ${ The goal is to construct a Hamiltonian path in the graph whose vertices are signed permutations and whose edges correspond exactly to these two operations.

codeforcescompetitive-programming
CF 103585K - Ceiba Tree

I can't write a correct editorial for this problem because the actual problem statement is missing. The prompt only contains: - Problem: Codeforces 103585K - Ceiba Tree - Empty Problem Statement - Empty Input - Empty Output Without the statement, it is impossible to determine…

codeforcescompetitive-programming
TAOCP 7.2.1.2 Exercise 34

The reviewer’s objections are all correct: the previous response never produced a single fully consistent alphametic, and in part (b) the proposed assignment is structurally impossible.

taocpmathematicsalgorithmsvolume-4math-hard
TAOCP 7.2.1.2 Exercise 33

Let the digits ${1,2,\dots,9}$ be arranged in some permutation, and let two cuts and a division sign be inserted to form an expression of the form $A + \frac{B}{C},$ where $A,B,C$ are positive integer...

taocpmathematicsalgorithmsvolume-4medium
TAOCP 7.2.1.2 Exercise 32

We correct the proof by replacing all heuristic exclusions with a finite structural analysis of the digit constraints.

taocpmathematicsalgorithmsvolume-4math-medium
CF 103585H - Sling Trees

Connection interrupted. Waiting for the complete answer

codeforcescompetitive-programming
CF 103585E - Truffula Trouble

The problem statement for Codeforces 103585E - Truffula Trouble is missing from your message, so I don’t have the actual task definition (inputs, outputs, or rules) needed to write a correct editorial.

codeforcescompetitive-programming
TAOCP 7.2.1.2 Exercise 31

We solve \frac{A}{10B+C}+\frac{D}{10E+F}+\frac{G}{10H+I}=1, \qquad \{A,\dots,I\}=\{1,\dots,9\}.

taocpmathematicsalgorithmsvolume-4math-medium
TAOCP 7.2.1.2 Exercise 30

A multiplicative alphametic is interpreted as a system of constraints over a partial injection $\varphi$ from letters to decimal digits, extended to numbers in base $10$ in the usual way.

taocpmathematicsalgorithmsvolume-4medium
CF 103585G - Perfect Cacti: Part 1

The problem statement for “Codeforces 103585G - Perfect Cacti: Part 1” is missing from your message, so I can’t reconstruct the actual graph structure, required output, or constraints reliably.

codeforcescompetitive-programming
TAOCP 7.2.1.2 Exercise 29

Let $n = s + t$ and let $C_{st}$ denote Chase’s sequence of all $(s,t)$-combinations of ${0,1,\dots,n-1}$ as described in Section 7.

taocpmathematicsalgorithmsvolume-4math-medium
TAOCP 7.2.1.2 Exercise 28

Let $n=s+t$ and consider genlex listings of $(s,t)$-combinations in index-list form $c_t c_{t-1}\dots c_1$ as defined by Algorithm $L$ in Section 7.

taocpmathematicsalgorithmsvolume-4math-medium
TAOCP 7.2.1.2 Exercise 27

An additive alphametic in the sense of Section 7.

taocpmathematicsalgorithmsvolume-4hard
TAOCP 7.2.1.2 Exercise 26

Solution to TAOCP 7.2.1.2 Exercise 26.

taocpmathematicsalgorithmsvolume-4medium
TAOCP 7.2.1.2 Exercise 25

Let $a_1,\dots,a_{10}$ be a permutation of $\{0,1,\dots,9\}$, with the constraint $a_i \neq 0$ for $i \in F$.

taocpmathematicsalgorithmsvolume-4math-medium
TAOCP 7.2.1.2 Exercise 24

Solution to TAOCP 7.2.1.2 Exercise 24.

taocpmathematicsalgorithmsvolume-4medium
TAOCP 7.2.1.2 Exercise 23

The previous solution failed because it implicitly treated an “alphametic identity” as a manipulable symbolic cancellation pattern, rather than a polynomial identity that must hold for all digit assig...

taocpmathematicsalgorithmsvolume-4math-medium
TAOCP 7.2.1.2 Exercise 22

The previous solution fails because it tries to separate bases via carry behavior, but an alphametic solution is not defined in terms of carries.

taocpmathematicsalgorithmsvolume-4math-simple
CF 103585D - Collecting Syrup

The task is about simulating how a sticky liquid spreads through a sequence of containers arranged in a line. Each container has a fixed capacity, and when liquid is poured into one container, it fills up to its limit and any excess immediately flows into the next container…

codeforcescompetitive-programming
TAOCP 7.2.1.2 Exercise 21

The previous solution fails at the point where it imports specific base-10 digits.

taocpmathematicsalgorithmsvolume-4math-medium
TAOCP 7.2.1.2 Exercise 20

We construct an explicit Hamiltonian path on the Cayley graph of the hyperoctahedral group $B_n$, whose vertices are signed permutations of $\{1,\dots,n\}$.

taocpmathematicsalgorithmsvolume-4medium
TAOCP 7.2.1.2 Exercise 19

Let $\alpha$ be a string of length $n=s+t$ on the alphabet ${+,-,0}$ satisfying the conditions of Exercise 29, so that $\alpha$ contains exactly $s$ signs and $t$ zeros.

taocpmathematicsalgorithmsvolume-4medium
TAOCP 7.2.1.2 Exercise 18

Let a string $\alpha$ consist of symbols in ${+, -, 0}$.

taocpmathematicsalgorithmsvolume-4medium
TAOCP 7.2.1.2 Exercise 17

Introduce an additional array $a'_{1}\ldots a'_{n}$ alongside Algorithm P, where at all times $a'_{k}=j$ if and only if $a_{j}=k$.

taocpmathematicsalgorithmsvolume-4medium
TAOCP 7.2.1.2 Exercise 16

Connection interrupted.

taocpmathematicsalgorithmsvolume-4medium