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tamnd's digital brain — notes, problems, research
41230 notes
Let $a_1 > a_2 > \cdots > a_m \ge 1$ be a partition of $n$ into distinct parts.
Let $a_1 a_2 \dots a_m$ be a partition written in nonincreasing form, and let $b_1 b_2 \dots b_m$ be its conjugate, so $b_j$ is the number of indices $i$ with $a_i \ge j$.
Let $$Fn(z)=prod{j=0}^{n-1}(1+z+cdots+z^{sj}), qquad left(!binom{S(n)}{k}!right)=[z^k]Fn(z).$$ Then $Fn=F{n-1}(1+z+cdots+z^{s{n-1}})$, so coefficient extraction gives $$left(!binom{S(n)}{k}!right) = sum{r=0}^{s{n-1}}left(!binom{S(n-1)}{k-r}!
I can’t write a correct editorial yet because the actual problem content for Codeforces 103034F - Mystery is missing from your prompt.
The problem statement is missing from your prompt (the “Problem / Input / Output” sections are empty), so there’s no way to correctly reconstruct Codeforces 103034D - Math Homework without guessing.
I can’t write a correct editorial yet because the actual problem statement for Codeforces 103034C - Two Hashes is missing from your prompt. Right now there’s no information about what the input represents, what “two hashes” refers to, or what needs to be computed.
I can’t write a correct editorial for “Codeforces 102992I - Interested in Skiing” without the actual problem statement. The structure you requested depends heavily on the precise mechanics of the task, and guessing would produce a misleading solution.
Let $\alpha$ be a partition of $n$, written in frequency form as $\alpha:\quad 1^{c_1} 2^{c_2} 3^{c_3}\cdots,$ where $c_j \ge 0$ and $\sum_{j\ge 1} j c_j = n$.
Let $a_1 \ge \cdots \ge a_n \ge 0$ and $a'_1 \ge \cdots \ge a'_n \ge 0$ be partitions of $n$.
The input is a square board where each position is either black, white, or empty. White stones can connect through up-down-left-right adjacency, forming clusters. A cluster survives only if at least one of its stones touches an empty cell.
Let $c_1,c_2,c_5,c_{10},c_{20},c_{50},c_{100}$ denote the numbers of coins of each denomination in cents.
Let $c_1c_2\cdots c_n$ be the part-count representation of a partition of $n$, so that $\sum_{j=1}^n j c_j = n.$ The colex order on partitions corresponds to lexicographic order on the reversed vector...
Let $U$ denote the set underlying the multicombinations (92). In the representation (6), each multicombination is a nonincreasing sequence $$dt ge d{t-1} ge cdots ge d1,qquad s ge dt,$$ and its complement with respect to $U$ is formed by taking the elements of $U$ not…
Let the Ferrers diagram of $a_1a_2\cdots a_m$ consist of cells $(i,j)$ with $1\le i\le m$ and $1\le j\le a_i$.
Let $U = {0,1,dots,n-1}$ with $n ge s+t$. Let $A subseteq binom{U}{s}$ and $B subseteq binom{U}{t}$ be cross-intersecting, meaning $alpha cap beta ne varnothing$ for all $alpha in A$ and $beta in B$.
The rim representation $(p_1 \ldots p_t, q_1 \ldots q_t)$ encodes the boundary (outer rim) of the Ferrers diagram of the partition $a_1 a_2 \ldots$ as an alternating sequence of maximal horizontal and...
The rim representation $(p_1 \ldots p_t, q_1 \ldots q_t)$ encodes the boundary (outer rim) of the Ferrers diagram of the partition $a_1 a_2 \ldots$ as an alternating sequence of maximal horizontal and...
Theorem W is proved in Section 7.2.1.3 under the standing assumption that the parameters $m1 le m2 le cdots le mn$.
The rim representation $(p_1 \ldots p_t, q_1 \ldots q_t)$ encodes the boundary (outer rim) of the Ferrers diagram of the partition $a_1 a_2 \ldots$ as an alternating sequence of maximal horizontal and...
Theorem W is proved in Section 7.2.1.3 under the standing assumption that the parameters $m1 le m2 le cdots le mn$.
A clutter on the ground set $[n]={0,1,\dots,n-1}$ is an antichain in the Boolean lattice: if $\alpha,\beta\in C$ and $\alpha\subseteq\beta$, then $\alpha=\beta$.
Let Theorem W be applied to the torus $T(m1,dots,mn)$ with cross order as in Section 7.2.1.3, and let $S$ be an initial segment in that order.
The prompt is missing the actual problem statement for “Codeforces 102979I - Integer Array Shuffle”, so there is not enough information to reconstruct the task, constraints, or required transformation.
I can’t reliably write a correct editorial for Codeforces 102979H - Hotspot-2 because the actual problem statement, constraints, and I/O format are missing from your prompt.
We are given a connected undirected graph with up to 100,000 vertices and edges. Each edge has a nonnegative weight.
Let Theorem W be applied to the torus $T(m1,dots,mn)$ with cross order as in Section 7.2.1.3, and let $S$ be an initial segment in that order.
The problem statement is missing, so I can’t safely derive the model, the solution, or any correctness argument yet.
We are given a line of pads placed on a straight horizontal axis. Each pad is located at an integer coordinate, and every pad is labeled with a number from 1 to n, with each label appearing exactly twice.
The problem statement is missing, so there isn’t enough information to reliably reconstruct what Codeforces 102979B (“Best Meeting Places”) is asking.
Let $mathcal{A}$ be a set of $t$-combinations and let $ $$kappat N = min{ where $partial mathcal{A}$ is the set of all $(t-1)$-subsets obtained by deleting one element from a member of $mathcal{A}$.
Let $T(m1,dots,m{n-1},m)$ be the $(n)$-dimensional torus equipped with cross order. Write elements as $(y,a)$ where $y in T(m1,dots,m{n-1})$ and $0 le a < m$ denotes the final component.
I’m missing the actual statement for Codeforces 102980D - “Побег из здания”, so I can’t reconstruct the problem logic or write a correct editorial yet.
I can’t write a correct editorial for this yet because the actual problem statement is missing. “Codeforces 102980C - Кибер-взлом” (Cyber-hack) isn’t included in your prompt, and I shouldn’t guess the task since even small misinterpretations would completely…
The problem statement for Codeforces 102984J - Setting Maps is missing from your prompt, so there is no way to correctly reconstruct the solution, constraints, or intended algorithm.
I can’t reliably write an editorial for this yet because the actual problem statement is missing. “Codeforces 102984K - Determinant” is just a title here, and different determinant problems on Codeforces vary a lot in structure, even if they share the same name.
Let $T(m1,dots,m{n-1},m)$ be the $(n)$-dimensional torus equipped with cross order. Write elements as $(y,a)$ where $y in T(m1,dots,m{n-1})$ and $0 le a < m$ denotes the final component.
I don’t have the actual statement of Codeforces 102984I - Selecting Points and Segments, and without it I’d be forced to invent the problem structure, which would make the editorial meaningless or incorrect.
I can’t write a correct editorial for this yet because the actual problem statement for Codeforces 102984H - Stone Catch Game is missing.
I can’t write a correct editorial for this yet because the actual problem statement is missing. Right now I only know the title, “Solo Tree Game,” but there’s no information about what the tree game rules are, what inputs are given, or what needs to be computed.
I can’t reliably write a correct Codeforces editorial here because the actual problem statement for 102984F - Rhythm Game is missing from your prompt.
I can’t write a correct editorial for this yet because the actual problem statement is missing. Right now we only have the title “Observer Game”, but no description of the rules, inputs, or outputs.
The problem statement isn’t included, so I can’t reliably reconstruct the task or produce a correct editorial. “Non-Decreasing Subarray Game” could correspond to multiple different CF-style mechanics (range queries, segment operations, game DP, etc.
We are given an $N times N$ grid of unit cells, all starting with beauty value zero. The system evolves through three kinds of operations applied over time. First, we may introduce horizontal or vertical cut lines across the grid.
I can’t produce a correct editorial for “Codeforces 102984A - Mango” yet because the actual problem statement is missing from your prompt.
Let $T(m1,dots,m{n-1},m)$ be the $(n)$-dimensional torus equipped with cross order. Write elements as $(y,a)$ where $y in T(m1,dots,m{n-1})$ and $0 le a < m$ denotes the final component.
Let $[n]={1,2,\dots,n}$.
Let $T(m1,ldots,m{n-1})$ be the $(n-1)$-dimensional torus with cross order $preceq$, and let $x = x1cdots x{n-1}$ be the $N$th element of this torus in cross order. Let $T(m1,ldots,m{n-1},m)$ be the extended torus.
I can’t write a correct editorial for this yet because the actual problem content is missing. Right now I only see the title “Verbose sandViches”, but no description of the task, input format, or output requirements.
I can’t write a correct editorial for “Codeforces 102985I - Sharing Cereal II” yet because the problem statement is missing from your prompt. Right now I have no information about: - what the input represents (arrays, graph, queries, etc.
Let $alpha$ be a $t$-combination, so $alpha$ is a $t$-element subset of ${0,1,dots,n-1}$. The operator $partialt alpha$ produces all $(t-1)$-combinations obtained by deleting one element of $alpha$. If $alpha={ct,dots,c1}$, then $$partialt alpha={alphasetminus{cj}mid 1le jle t}.
I can’t write a correct editorial for this yet because the actual problem statement is missing. “Codeforces 102985H - Coprime Ribs” isn’t a standard publicly known problem in a way I can reliably reconstruct, and without the statement I would be guessing the entire…
I can’t write a correct editorial for “Codeforces 102985F - Norman’s N&N’s” because the actual problem statement is missing.
We are given a rectangular pizza placed on a coordinate plane. The bottom-left corner can be thought of as the origin, and the pizza spans a width and height. The chef then makes a set of horizontal cuts and a set of vertical cuts.
I can absolutely write this editorial in your required Codeforces style, but I’m missing the most important ingredient: the actual problem statement.
Let $alpha$ be a $t$-combination, so $alpha$ is a $t$-element subset of ${0,1,dots,n-1}$. The operator $partialt alpha$ produces all $(t-1)$-combinations obtained by deleting one element of $alpha$. If $alpha={ct,dots,c1}$, then $$partialt alpha={alphasetminus{cj}mid 1le jle t}.
We start with a single node and then add nodes one by one. When node i is added, it attaches to one of the previous nodes j with probability proportional to a given weight aj. Once the parent j is chosen, the edge length between i and j is defined as ci + cj.
I don’t have the actual statement for Codeforces 102986H - Coprime Ribs in your prompt, so I can’t reliably reconstruct the problem or write a correct editorial.
I’m missing the actual problem statement for Codeforces 102986F - Norman’s N&N’s, so I can’t reliably reconstruct the solution or write a correct editorial.
I’m missing the actual problem statement for Codeforces 102986D - Peter Piper Picked the Perfect Piece of Pizza, so I can’t safely reconstruct the intended model, constraints, or solution.
The prompt is missing the actual problem content. Right now we only have the title “Codeforces 102986E - Food Donations” but no description, input, output, or constraints.
The problem describes a person who has a list of favorite foods and is given a sequence of foods they eat over time.
I can’t reliably write a correct editorial for Codeforces 102986C - Spice Ratios without the actual problem statement.
Let $C$ be a simplicial complex on a fixed vertex set $V$ with $|V|=4$.
We are modeling a situation where a person repeatedly produces probabilistic “fireworks batches” over time. Each production attempt takes a fixed amount of time, and each produced firework independently has a small probability of being “perfect”.
We are building a walk on an infinite grid starting from the origin. Each move is one unit in one of the four cardinal directions: right, left, up, or down, with given available counts for each direction. The final walk must use exactly all moves.
I can’t write a correct editorial for this yet because the actual problem statement is missing. Right now I only have the title “Pointer Analysis”, but nothing about: what the input contains, what transformations are performed, or what needs to be computed.
The problem statement is missing from your prompt, so there’s no way to correctly derive the solution, constraints, or algorithmic structure for “Codeforces 102993I - Valuable Forests”.
Let $S(n,t,r)$ denote the set of Ising configurations from exercise 13 with parameters $n,t,r$ and with the additional restriction $a0=0$. Each configuration is a binary string $a{n-1}dots a1a0 in {0,1}^n,$ satisfying the constraints defining exercise 13 together with $a0=0$.
I can’t write a correct Codeforces editorial without the actual problem statement. Right now, the prompt only includes the template, but “Dividing” (102993H) itself is missing, so there’s no way to know: - what is being divided (arrays, numbers, graph components, etc.
I don’t have the actual statement for Codeforces 102993G - Topo Counting in your message, so I can’t reliably reconstruct the problem, constraints, or intended solution path.
The editorial can’t be written yet because the actual problem statement for Codeforces 102993F - Tokens on the Tree is missing.
The problem statement is missing from your prompt, so I can’t reliably reconstruct the task or write a correct Codeforces-style editorial.
I can’t reliably reconstruct the full problem from just the name and ID, and for a Codeforces editorial that would mean guessing the core task, which would make the entire solution and correctness discussion meaningless.
The problem statement for Codeforces 102993B - Mask Allocation is missing from your prompt, so there is no way to reconstruct the logic, constraints, or intended algorithm correctly.
The problem statement section is empty, so there isn’t enough information to reconstruct what “A National Pandemic” is actually asking.
Let $S(n,t,r)$ denote the set of Ising configurations from exercise 13 with parameters $n,t,r$ and with the additional restriction $a0=0$. Each configuration is a binary string $a{n-1}dots a1a0 in {0,1}^n,$ satisfying the constraints defining exercise 13 together with $a0=0$.
Let $S(n,t,r)$ denote the set of Ising configurations from exercise 13 with parameters $n,t,r$ and with the additional restriction $a0=0$. Each configuration is a binary string $a{n-1}dots a1a0 in {0,1}^n,$ satisfying the constraints defining exercise 13 together with $a0=0$.
I can’t produce a correct editorial yet because the actual problem statement for Codeforces 102994M - Travel Dream is missing from your prompt.
I can’t reliably write a correct Codeforces editorial for “102994L - Landlord” because the actual problem statement is missing from your prompt.
I can’t reliably write an editorial for “Codeforces 102994K - Data Structure” because the actual problem statement is missing from your prompt.
I can’t produce a correct Codeforces-style editorial yet because the actual problem content for 102994J - Gaokao is missing from your prompt.
The problem statement is missing from your prompt, so I can’t reliably reconstruct what Codeforces 102994H is asking. For a geometry problem especially, the entire solution structure depends on very specific details (points, segments, distances, queries, constraints).
Let $n=s+t$ as in (1), and let an $(s,t)$-combination be written in the form $ct cdots c2 c1$ satisfying (3), that is $n ct cdots c2 c1 ge 0.
I can’t reliably write a correct Codeforces 102994G editorial from what you’ve provided because the actual problem content (rules of “Blackjack”, input format, and required output) is missing.
I can’t write a correct editorial for this yet because the actual problem statement for Codeforces 102994F - Girlfriend is missing from your prompt. Right now I only see the template sections (Input/Output are empty), which isn’t enough to reconstruct the problem.
I can’t reliably write a correct editorial for Codeforces 102994E - Road Construction without the actual problem statement.
I can’t responsibly write a correct editorial for this yet because the actual problem statement is missing. Right now I only have the title “102994B - Gifted Composer”, but no description of what the input represents, what is being optimized or computed, or even the…
I’m missing the actual problem statement for Codeforces 102994A - Everyone Loves Playing Games, so I can’t reliably reconstruct the task or derive the correct algorithm.
Let $n=s+t$ as in (1), and let an $(s,t)$-combination be written in the form $ct cdots c2 c1$ satisfying (3), that is $n ct cdots c2 c1 ge 0.
I can’t reliably write a correct editorial for Codeforces 103003E - Dream and the Multiverse because the actual problem statement is missing from your prompt.
The problem statement section is empty, so there’s not enough information to write a correct editorial. “Modular Exponentiation” could mean several different tasks on Codeforces: single query fast power computation, multiple queries with different moduli, precomputation…
I can’t write a correct Codeforces editorial for 103003B - DDDFT yet because the actual problem statement is missing. Right now I don’t know: - what the input represents, - what transformation or computation is required, - or what the output should be.
The exercise refers to the “basic compression lemma (85)”, but the statement of (85) is not included in the provided excerpt of Section 7.2.1.3.
I can’t write a correct editorial for this yet because the actual problem statement is missing. “Codeforces 103029D - John and pizza” isn’t enough on its own to reconstruct the task reliably, and guessing would almost certainly produce a wrong solution and misleading…
I can’t produce a correct editorial for this problem yet because the actual problem statement is missing. “Codeforces 103029C - John, Katya, no nuts” doesn’t include any description of the input/output or the task, and without that there’s nothing concrete to restate…
I’m missing the actual problem statement for Codeforces 103029A - John and nuts in your prompt, so I can’t safely reconstruct the intended solution or write a correct editorial.
The problem statement is missing, so I can’t reliably reconstruct what “Подсчет хештегов” (Hashtag counting) is asking for or what the required output format is.
The exercise refers to the “basic compression lemma (85)”, but the statement of (85) is not included in the provided excerpt of Section 7.2.1.3.
The problem statement for Codeforces 103031E - “Загадочное устройство” is missing from your prompt, so I don’t have the actual rules, inputs, or required output to base an editorial on.
I don’t have the actual problem statement for Codeforces 103031D - Government Census in your message, and I can’t reliably reconstruct it from the ID alone without risking inventing details.