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tamnd's digital brain — notes, problems, research

41624 notes

CF 105745B - Cache

I can’t reliably write a correct Codeforces editorial for 105745B - Cache without the actual problem statement. Codeforces “Cache” could refer to several completely different problems (LRU simulation, query caching, prefix reuse, etc.

codeforcescompetitive-programming
CF 105335B - Back in the Day

The input is a sequence of digits from 2 to 9 that comes from an old multi-tap phone keypad. Each digit corresponds to a group of letters, and a letter is produced by pressing that digit multiple times in a row.

codeforcescompetitive-programming
TAOCP 7.1.2 Exercise 47

Let $f : \{0,1\}^n \to \{0,1\}^m$.

taocpmathematicsalgorithmsvolume-4math-medium
CF 105335D - Disinfection Patch

We are given two sets of points in the plane. The first set represents “disinfection drops”, and the second set represents bacteria locations. We are allowed to choose three parameters: a scaling factor $S ge 0$, and a translation vector $(X, Y)$.

codeforcescompetitive-programming
CF 105335C - Cattering

We are given a rectangular table describing how much each cat enjoys each type of food. There are N cats and M food types, with M at least N. Each cat must be assigned a different food type, so no food is reused, and every cat gets exactly one food.

codeforcescompetitive-programming
TAOCP 7.1.2 Exercise 46

Let $s=\lfloor 2^n/n\rfloor$.

taocpmathematicsalgorithmsvolume-4hm-medium
TAOCP 7.1.2 Exercise 45

The expression $n^2(n+1)^2\cdots (n+r-1)^2$ treats the construction of a Boolean chain as if step $i$ allows an arbitrary independent choice of an ordered pair of earlier objects, with $(n+i-1)$ avail...

taocpmathematicsalgorithmsvolume-4hm-medium
CF 105292M - Melting

Sure. Please provide the Codeforces problem statement (or the problem link/contest ID and problem letter), and I'll write a complete competitive-programming editorial including: - Problem restatement - Key observations - Derivation of the solution - Proof of correctness - Time…

codeforcescompetitive-programming
TAOCP 7.1.2 Exercise 44

Let inputs be $(x_1,\ldots,x_n)$ and $(y_1,\ldots,y_n)$, and define binary addition as in (25), producing sum bits $(z_1,\ldots,z_n)$ and carry bits $(c_1,\ldots,c_{n+1})$ with $c_1=0$.

taocpmathematicsalgorithmsvolume-4hard
TAOCP 7.1.2 Exercise 43

Let the transducer be applied to input $a_1\cdots a_n$, producing outputs $b_1\cdots b_n$, with state sequence $q_0,q_1,\ldots,q_n$ defined by q_j = d(q_{j-1},a_j), \quad b_j = c(q_{j-1},a_j), as requ...

taocpmathematicsalgorithmsvolume-4hard
TAOCP 7.1.2 Exercise 42

Let u_k = x_k \wedge y_k,\qquad v_k = x_k \oplus y_k,\qquad 0 \le k < n, and let $c_k$ be the carry bits in binary addition.

taocpmathematicsalgorithmsvolume-4hard
TAOCP 7.1.2 Exercise 41

Let $A(n)$ denote the number of binary gates in an $n$-bit conditional-sum adder constructed recursively as described, and let $D(n)$ denote its depth.

taocpmathematicsalgorithmsvolume-4math-medium
TAOCP 7.1.2 Exercise 38

Let the inputs be $x_1,\dots,x_n \in \{0,1\}$, and let t=\sum_{j=1}^n x_j be the number of ones.

taocpmathematicsalgorithmsvolume-4medium
CF 105292K - King Game

We have two pieces on a $300 times 300$ board. A move chooses one piece at position $(x,y)$ and moves it to any strictly smaller position inside the rectangle $[1,x] times [1,y]$. The destination cannot be the current square and cannot be occupied by the other piece.

codeforcescompetitive-programming
CF 105292G - Graph Problem

We are given $N$ circular intervals on a circle whose coordinates are numbered from $0$ to $2N-1$. Each vertex of the graph corresponds to one interval. Two vertices are adjacent when their intervals overlap.

codeforcescompetitive-programming
CF 105292A - Akari

We are given a rectangular Akari board consisting of empty cells . and walls . A light bulb can be placed only on an empty cell. Its light travels horizontally and vertically until it reaches a wall or the edge of the board.

codeforcescompetitive-programming
TAOCP 7.1.2 Exercise 39

The flaw in the previous solution is the separation of “selector construction” and a later “global OR stage.

taocpmathematicsalgorithmsvolume-4math-medium
TAOCP 7.1.2 Exercise 37

Let $p_k = x_1 \wedge x_2 \wedge \cdots \wedge x_k$.

taocpmathematicsalgorithmsvolume-4math-hard
TAOCP 7.1.2 Exercise 35

Solution to TAOCP 7.1.2 Exercise 35.

taocpmathematicsalgorithmsvolume-4medium
CF 105756B - Maximum Combo

I can write the editorial, but the problem statement for Codeforces Gym 105756B appears to be inconsistent with its samples. The statement says that jumping from portal i to portal j gives i j points, starting from portal 1.

codeforcescompetitive-programming
CF 105756C - F1 Glory

I don’t have the actual problem statement for Codeforces 105756C - F1 Glory in your prompt, and it’s required to write a correct editorial.

codeforcescompetitive-programming
CF 105756A - Least Penalty

Sure - but I’ll need the problem first. Please paste the Codeforces problem statement (or at least the link / full text).

codeforcescompetitive-programming
CF 105757M - Alternating sum

We are given an array of integers and we need to support operations involving the “alternating sum” over segments of this array.

codeforcescompetitive-programming
CF 105757L - Tree Harmony

We have a rooted tree with root 1. Every vertex stores a value. For each query (u, v), we need to decide whether v lies inside the subtree of u and whether the vertices that remain after removing the whole subtree of v from the subtree of u can be paired so that every pair…

codeforcescompetitive-programming
CF 105757I - Min Xor Subarray

We are given a sequence of integers and we are allowed to pick any contiguous segment of it. For each segment we compute the bitwise XOR of all its elements, and the task is to find the smallest XOR value achievable among all possible segments.

codeforcescompetitive-programming
TAOCP 7.1.2 Exercise 36

The error in the previous writeup is a conflation of _schedule phases_ with _critical-path length_.

taocpmathematicsalgorithmsvolume-4math-hard
CF 105767F - Mega Polynomial

We are given two polynomials. The first one is a linear polynomial $$f(x)=Ax+B$$ and the second one has only two non-zero terms: $$g(x)=Cx^n+Dx^{n-1}.

codeforcescompetitive-programming
CF 105767G - Max-Min Madness

Sure - I can do that. Please paste the Codeforces problem statement (or at least the problem link / full text). If there are constraints or samples, include those too.

codeforcescompetitive-programming
CF 105767E - GCD and LCM in Perfect Sync

I can’t write a correct Codeforces editorial without the actual problem statement. Right now the “Problem Statement / Input / Output” sections are empty, so there’s no way to reconstruct: - what objects are being manipulated - what “GCD and LCM in perfect sync”…

codeforcescompetitive-programming
CF 105767D - Array Forge

Sure-please paste the full Codeforces problem statement (or at least the problem link / contest + problem letter).

codeforcescompetitive-programming
CF 105767A - Submission Bait II

The task is to build an array of length n where every value is between 1 and 2n, and no value in the array can divide another value at a different position. The actual values do not matter beyond satisfying these two rules, so any valid construction is accepted.

codeforcescompetitive-programming
CF 105767C - Kaosar loves Polynomials

I’m missing the actual statement for Codeforces 105767C - Kaosar loves Polynomials, so I can’t reliably reconstruct the intended model, constraints, or even what is being computed. Right now you’ve provided only the formatting instructions, not the problem itself.

codeforcescompetitive-programming
CF 105767B - Subtractonacci

Sure - I can do that, but I need the problem first. Please paste the full Codeforces problem statement (or at least the key parts: input/output format, constraints, and statement). If you also have a link or contest/problem ID, that works too.

codeforcescompetitive-programming
CF 105775F - Fawanis Ramadan

Got it. Please provide the Codeforces problem statement (or at least the link / full text), and I’ll write a complete competitive programming editorial. If you want a specific style, tell me too-e.g.

codeforcescompetitive-programming
CF 105775L - Maze Chase

Sure. Please provide the Codeforces problem statement (or at least the problem name, link, constraints, and examples), and I’ll write a detailed competitive programming editorial. I’ll structure it like a typical Codeforces editorial: 1. Problem Restatement 2.

codeforcescompetitive-programming
CF 105775K - Yet Another Swap Task

The problem statement is missing from your prompt, so there’s no way to reconstruct a correct editorial without guessing the task.

codeforcescompetitive-programming
CF 105775J - Rock Paper Scissors

Sure. Please provide the Codeforces problem statement (or a link, problem name, and constraints), and I’ll write a detailed competitive programming editorial covering: - Problem restatement and observations - Key idea / intuition - Proof of correctness - Algorithm -…

codeforcescompetitive-programming
CF 105775I - Vanishing Island

I don’t have the actual statement for Codeforces 105775I - Vanishing Island in the prompt (the problem content sections are empty), so there’s nothing concrete to base the editorial on yet.

codeforcescompetitive-programming
CF 105775H - Hamming Guess

This is an interactive problem where the judge hides a number of golden coins, represented as an integer from 1 to 10^9. Your program can repeatedly propose a number, and the judge answers with the Hamming distance between the proposed number and the hidden number.

codeforcescompetitive-programming
CF 105775G - Guess The Permutation

I can’t write a correct editorial yet because the actual problem statement is missing. Right now I only see the title “105775G - Guess The Permutation”, but there are no rules describing: - what interaction or input format is given - what operations are allowed (queries…

codeforcescompetitive-programming
CF 105775E - Swap Task

Sure. Please provide the Codeforces problem statement (or at least the problem name, constraints, and examples), and I’ll write a detailed competitive programming editorial. I can structure it like a typical Codeforces editorial: 1. Problem Restatement 2. Key Observations 3.

codeforcescompetitive-programming
CF 105775D - Max Diversity, No Superiority

I’m missing the actual problem statement for Codeforces 105775D - Max Diversity, No Superiority. Right now only the title is provided, and there’s no information about what the input/output means or what “diversity” or “superiority” refer to in this context.

codeforcescompetitive-programming
CF 105775A - Alibaba and Forty Thieves

The problem works with a main array, and a stream of additional arrays that we store over time. Later, we receive queries that ask us to compare a subarray of the main array against all stored arrays, but the comparison is not positional.

codeforcescompetitive-programming
CF 105775B - Bad Sindibad

I can write the full editorial, but the problem statement you provided is missing the actual shape image. For Codeforces 105775B - Bad Sindibad, the exact polyomino shape is essential because the entire solution depends on the possible placements and the state transitions in…

codeforcescompetitive-programming
CF 105775C - The Tale of the Magical Lantern Grid

The problem statement for Codeforces 105775C - The Tale of the Magical Lantern Grid is missing from your prompt, so I can’t reconstruct the solution or write a correct editorial without risking inventing details.

codeforcescompetitive-programming
TAOCP 7.1.2 Exercise 33

Let $m_i$ denote the minterm corresponding to the binary vector of $i$, for $0 \le i < 2^n$, where $m_i$ is the conjunction of literals $x_k$ or $\bar{x}_k$ according to the binary expansion of $i$.

taocpmathematicsalgorithmsvolume-4hm-medium
CF 105780J - Dimensional Flower

The flower grows on a d-dimensional integer grid. It starts at the origin, and each second it moves exactly one unit along one coordinate axis. The direction must always be away from the origin along that axis.

codeforcescompetitive-programming
CF 105780I - Pikmin Bloom

I can’t write a correct editorial yet because the actual problem statement for “Codeforces 105780I - Pikmin Bloom” isn’t included in your prompt.

codeforcescompetitive-programming
CF 105780H - Gone with the Wind

I can’t reliably write an editorial for this without the actual problem statement. “Codeforces 105780H - Gone with the Wind” isn’t something I can reconstruct from metadata alone, and guessing would almost certainly produce a wrong or unrelated solution.

codeforcescompetitive-programming
CF 105780E - Walrus Wallflowers

The garden is an n x n grid. Some cells already contain flowers. During the process, cells can gain flowers or pairs of cells can be joined by underground tunnels.

codeforcescompetitive-programming
CF 105780G - Paper Bouquet

Sure-please share the Codeforces problem statement (or at least the link / problem name). Once I have it, I’ll write a full competitive programming editorial: intuition, key observations, algorithm, proofs where needed, complexity, and implementation notes.

codeforcescompetitive-programming
CF 105780F - X Marks the Pot

I can’t produce a correct editorial yet because the actual statement for Codeforces 105780F - “X Marks the Pot” is missing from your prompt.

codeforcescompetitive-programming
CF 105780D - Florescent Constellations

Sure - please paste the Codeforces problem statement (or at least the link / full text). Once I have it, I’ll write a proper competitive programming editorial with: - Problem summary - Key observations - Full solution intuition - Correctness explanation - Complexity analysis…

codeforcescompetitive-programming
TAOCP 7.1.2 Exercise 34

The construction must be repaired at the output stage and the definition of the suffix information must be made precise.

taocpmathematicsalgorithmsvolume-4medium
CF 105780A - Garden Planning

I’m missing the actual problem statement for Codeforces 105780A - Garden Planning, and without it I can’t responsibly reconstruct the solution or write a correct editorial.

codeforcescompetitive-programming
CF 105780B - Picture Perfect

I do not want to invent a solution for the wrong problem.

codeforcescompetitive-programming
CF 105780C - Flower Dance

I can’t write a correct editorial for that problem yet because the actual statement is missing from your prompt. “Codeforces 105780C - Flower Dance” alone isn’t enough to reconstruct the task reliably.

codeforcescompetitive-programming
CF 105782J - Dimensional Flower

We are given a system where a “flower” starts at the origin in a $d$-dimensional integer grid. Time progresses in discrete steps, and at each step the flower extends its shape by moving one unit along exactly one of the coordinate axes.

codeforcescompetitive-programming
CF 105782I - Pikmin Bloom

I can’t write a correct Codeforces-style editorial without the actual problem statement. Right now, the “Problem Statement / Input / Output” sections are empty, so there’s no information about: what the process is, what is being computed, or even the constraints that…

codeforcescompetitive-programming
CF 105782H - Gone with the Wind

I can write the full editorial in the requested format, but I need the actual problem statement first. The statement section in your prompt is empty, and I could not reliably identify the problem details for Codeforces 105782H “Gone with the Wind” from the available…

codeforcescompetitive-programming
CF 105782E - Walrus Wallflowers

We are given an evolving system on a grid of cells where each cell may or may not contain a flower. Over time, two kinds of actions are applied: a cell can be turned into a flower cell, and a connection can be added between two cells.

codeforcescompetitive-programming
CF 105782G - Paper Bouquet

I can’t write a correct editorial yet because the actual problem content is missing. Right now I only see the title “105782G - Paper Bouquet”, but there is no description of: what the input is, what needs to be computed, or any constraints.

codeforcescompetitive-programming
CF 105782D - Florescent Constellations

I can write the full editorial, but the actual problem statement is missing from the prompt. The sections labeled “Problem Statement”, “Input”, and “Output” are empty, and I do not want to invent the rules, constraints, or algorithm for a geometry problem and give…

codeforcescompetitive-programming
CF 105782F - X Marks the Pot

I can’t write a correct Codeforces-style editorial for this problem yet because the actual problem statement (what the input describes, what needs to be computed, and constraints) is missing from your prompt.

codeforcescompetitive-programming
CF 105782B - Picture Perfect

I can’t write a correct editorial for “Codeforces 105782B - Picture Perfect” because the actual problem statement is missing from your message.

codeforcescompetitive-programming
CF 105782C - Flower Dance

I can’t write a correct editorial for this yet because the actual problem statement is missing. “Codeforces 105782C - Flower Dance” doesn’t come with any details in your prompt, and I don’t have the ability to reliably reconstruct the problem from the title alone.

codeforcescompetitive-programming
CF 105782A - Garden Planning

I can write the editorial, but I need the full problem statement first. The Codeforces page for 105782A - Garden Planning is available, but the statement details are not included in your prompt, and I need the exact input/output behavior and constraints to produce a correct…

codeforcescompetitive-programming
CF 105783F - Balloons

I don’t have the actual statement for Codeforces 105783F - Balloons in your prompt, so I can’t reliably reconstruct the problem or produce a correct editorial.

codeforcescompetitive-programming
CF 105783D - Coprime Sums

We are given a multiset of positive integers and need to evaluate a sum over all unordered pairs of elements. For each pair, we look at whether the two numbers are coprime, meaning their greatest common divisor is 1.

codeforcescompetitive-programming
CF 105783E - Blackboard

I don’t want to invent an algorithm for the wrong “Blackboard” problem.

codeforcescompetitive-programming
CF 105783C - Encoding

We are given a line of boxes, each box contains a positive number of candies and has a color among three possible values. A person starts at a fixed position on this line and wants to collect candies by repeatedly moving to some box and eating all candies from it instantly.

codeforcescompetitive-programming
CF 105783A - Length of the Path

I can write the editorial, but the full response you requested is very long and requires the exact accepted implementation and test cases. I found the problem statement for Codeforces Gym 105783A, “Length of the Path”, which matches the described hiking path problem.

codeforcescompetitive-programming
CF 105783B - Many Tasks

I cannot reliably recover the exact original statement of Codeforces 105783B “Many Tasks” from public archives, and this problem ID does not correspond to a standard Codeforces contest problem with a stable mirror.

codeforcescompetitive-programming
TAOCP 7.1.2 Exercise 32

The correct argument must stay within the structure of the explicit solution given in (30), and must not invoke characteristic polynomials or linear constant-coefficient recurrences.

taocpmathematicsalgorithmsvolume-4hm-medium
CF 105786J - Making 0s

Codeforces 105786J: Making 0s

codeforcescompetitive-programming
TAOCP 7.1.2 Exercise 31

Solution to TAOCP 7.1.2 Exercise 31.

taocpmathematicsalgorithmsvolume-4medium
TAOCP 7.1.2 Exercise 30

Let s(n)=s\!

taocpmathematicsalgorithmsvolume-4math-medium
CF 105786E - Good Array

Codeforces 105786E: Good Array

codeforcescompetitive-programming
CF 105786L - Quicksort

I can’t write a correct Codeforces-style editorial for 105786L - Quicksort without the actual problem statement. Right now the prompt only gives the title, but there are multiple possible problems that could reasonably be named “Quicksort” (counting swaps, simulating…

codeforcescompetitive-programming
CF 105786K - Hydra

I can’t reliably write a correct editorial for “Codeforces 105786K - Hydra” because the problem statement is missing here. Right now I don’t have the definition of the input, what operations are allowed, or what needs to be computed.

codeforcescompetitive-programming
CF 105786I - GCD Splicing

I can’t reliably reconstruct the full statement of Codeforces 105786I “GCD Splicing” from the problem code alone, and I don’t want to guess and give you a completely incorrect editorial.

codeforcescompetitive-programming
CF 105786H - Shortest Subarray

Sure. Please provide the Codeforces problem statement (or at least the problem name, constraints, and examples), and I’ll write a competitive programming editorial in the style of an official Codeforces explanation.

codeforcescompetitive-programming
CF 105786G - Miyamura and Cake

Got it. Please send the Codeforces problem (statement + constraints, or a link / screenshot text), and I’ll write a full competitive programming editorial for it. If you want a specific style (e.g.

codeforcescompetitive-programming
CF 105786D - Strictly Increasing

The task is about maintaining whether a sorted sequence has enough empty integer positions to insert exactly k new values. The original array is supposed to be strictly increasing, but after each update one element may change, so the array can temporarily become invalid.

codeforcescompetitive-programming
TAOCP 7.1.2 Exercise 29

The missing point in the previous solution is the justification that the block-combining circuit from Exercise 27 has constant depth.

taocpmathematicsalgorithmsvolume-4math-hard
CF 105786F - 7s

Sure-please paste the Codeforces problem statement (or at least the link / key parts). Once I have it, I’ll write a full competitive programming editorial with: - problem breakdown - key observations - step-by-step solution - complexity analysis - edge cases - reference…

codeforcescompetitive-programming
TAOCP 7.1.2 Exercise 24

The previous solution fails at the only point where it matters: it does not establish a lower bound for tree complexity.

taocpmathematicsalgorithmsvolume-4research
CF 105786C - Combination Lock

Got it - I’ll write it in Codeforces editorial style (clear intuition, step-by-step reasoning, edge cases, complexity, etc.). Please send the full problem statement (or a link / screenshot text).

codeforcescompetitive-programming
CF 105786A - Shortest Substring

The problem statement is missing from your prompt, so I don’t have enough information to write a correct editorial.

codeforcescompetitive-programming
CF 105786B - Alya and Permutation Revisited

Sure. Please provide the Codeforces problem statement (or a link, problem name, and constraints), and I’ll write a detailed competitive programming editorial covering: - Problem restatement and observations - Key insights / intuition - Proof of correctness - Algorithm…

codeforcescompetitive-programming
CF 105788I - Interns

The editorial can’t be written yet because the actual problem statement is missing. Right now there’s no description of what “105788I - Interns” is asking for, so there’s no way to reconstruct: - what the input represents, - what transformation or computation is…

codeforcescompetitive-programming
CF 105788H - Optimal Assembly

I can’t write a correct editorial for “Codeforces 105788H - Optimal Assembly” because the actual problem statement is missing from your prompt.

codeforcescompetitive-programming
CF 105788G - Metro in Ufa

Sure. Please provide the Codeforces problem statement (or a link/name of the problem), and I’ll write a detailed competitive programming editorial. I can structure it like a typical Codeforces editorial: 1. Problem Restatement 2. Key Observations 3. Main Idea / Insight 4.

codeforcescompetitive-programming
CF 105788F - Mathematics Olympiad

I don’t have the actual statement of Codeforces 105788F (“Mathematics Olympiad”) in your message, so I can’t safely reconstruct the problem or derive a correct solution without guessing.

codeforcescompetitive-programming
CF 105788E - Captivity

I cannot produce a correct editorial for Codeforces 105788E - Captivity yet because the actual problem statement is missing, and it is not retrievable from the provided context or standard public mirrors.

codeforcescompetitive-programming
CF 105788D - There Was Nothing to Do

I will keep the requested senior-engineer style and include a correct Python implementation based on the actual problem.

codeforcescompetitive-programming
CF 105788C - Rebellion of the Vacuum Robots

The problem statement is missing from your prompt, so I don’t have the actual task description, inputs, or required output for “Codeforces 105788C - Rebellion of the Vacuum Robots”.

codeforcescompetitive-programming
CF 105788B - You need to buy a new SSD...

We can’t honestly write a correct Codeforces editorial yet because the actual problem statement for “105788B - You need to buy a new SSD...” is not included in your prompt, and it is not a standard publicly indexed Codeforces problem with a reliably retrievable statement.

codeforcescompetitive-programming
CF 105788A - Flor's Problems

Sure. Please provide the Codeforces problem statement (or a link, problem name, and constraints), and I’ll write a competitive programming editorial with: - Problem restatement - Key observations - Intuition behind the solution - Proof of correctness - Complexity analysis -…

codeforcescompetitive-programming
CF 105792G - Реформа

I’m missing the actual problem statement for Codeforces 105792G - “Реформа”, so I can’t responsibly derive the solution or write a correct editorial yet. Please paste the full statement (or even a screenshot/text dump of the input, output, and description).

codeforcescompetitive-programming