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Problem StatementA box contains $N$ balls, each with an integer between $1$ and $M-1$ written on it. For $i = 1, 2, \ldots, N$, the integer written on 阅读全文
posted @ 2023-01-03 16:37
灰鲭鲨
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Problem StatementWe have a directed graph with $N$ vertices, called Vertex $1$, Vertex $2$, $\ldots$, Vertex $N$. For each pair of integers such that 阅读全文
posted @ 2023-01-02 20:24
灰鲭鲨
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Problem StatementYou are given an undirected tree with $N$ vertices. Let us call the vertices Vertex $1$, Vertex $2$, $\ldots$, Vertex $N$. For each $ 阅读全文
posted @ 2023-01-02 19:59
灰鲭鲨
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杜教筛是拿来求积性函数前缀和的东西 $h=fg$ $s(n)=\sum\limits_{i=1}^ng(i)$ 而杜教筛可以在 $O(n^{\frac 23})$ 的复杂度内求出 $s(n)$，前提是存在两个很好求前缀和的函数 $f$ 和 $h$ 满足 $h=fg$ $\sum\limits_{i= 阅读全文
posted @ 2023-01-02 18:44
灰鲭鲨
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Problem StatementTakahashi has $A$ apple seedlings, $B$ banana seedlings, and $C$ cherry seedlings. Seedlings of the same kind cannot be distinguished 阅读全文
posted @ 2023-01-02 17:25
灰鲭鲨
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题目 求 $f(a,b,c,n)=\sum\limits_{i=0}^n\lfloor\frac{ai+b}c\rfloor$ 题解 当 $a\ge c$ 或 $b\ge c$ 时， $\begin{aligned} \sum\limits_{i=0}^n\lfloor\frac{ai+b}c\rf 阅读全文
posted @ 2022-12-31 17:44
灰鲭鲨
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Problem StatementWe have a grid with $H$ rows and $W$ columns. Each square is painted either white or black. For each integer pair $(i, j)$ such that 阅读全文
posted @ 2022-12-23 20:53
灰鲭鲨
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Problem StatementWe have a rooted tree with $N$ vertices numbered $1,2,\dots,N$. The tree is rooted at Vertex $1$, and the parent of Vertex $i \ge 2$ 阅读全文
posted @ 2022-12-23 20:46
灰鲭鲨
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Problem StatementIn a string fair, they determine the beauty of a non-empty string $S$ consisting of lowercase English letters. The beauty of string $ 阅读全文
posted @ 2022-12-23 20:14
灰鲭鲨
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Problem StatementYou are given an integer sequence $A = (A_1, \dots, A_N)$ of length $N$. Find the number, modulo $998244353$, of permutations $P = (P 阅读全文
posted @ 2022-12-23 17:05
灰鲭鲨
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