大学物理急救指北

Problem

You are given sequences of length \(N\), \(A=(A_1,A_2,\ldots,A_N)\) and \(B=(B_1,B_2,\ldots,B_N)\).

You are also given \(Q\) queries to process in order.

There are three types of queries:

• 1 l r x : Add \(x\) to each of \(A_l, A_{l+1}, \ldots, A_r\).
• 2 l r x : Add \(x\) to each of \(B_l, B_{l+1}, \ldots, B_r\).
• 3 l r : Print the remainder of \(\displaystyle\sum_{i=l}^r (A_i\times B_i)\) when divided by \(998244353\).

Problem

For a positive integer \(N\), let \(V_N\) be the integer formed by concatenating \(N\) exactly \(N\) times.

More precisely, consider \(N\) as a string, concatenate \(N\) copies of it, and treat the result as an integer to get \(V_N\).

For example, \(V_3=333\) and \(V_{10}=10101010101010101010\) .

Find the remainder when \(V_N\) is divided by \(998244353\).

Hexo博客Next主题更换cdn加速访问

有时候访问我的博客时，总是会出现cdn.jsdelivr.net无法访问或者访问速度过慢的情况。我的博客园使用的是BNDong/Cnblogs-Theme-SimpleMemory主题，也遇到的这样的情况。经过我的一番折腾之后，将js文件转移到了我自己的OSS中，并且又经过了我的一番折腾之后，设置好了跨域资源共享（CORS）策略，让我的博客访问的时候不会时好时坏了。

现在我搭建了Hexo博客，使用Next主题，其中也使用了很多jsdelivr的托管文件。有时候别人会出现访问慢、卡、进不去的情况。我打算也更换成我的OSS。

好在Next主题配置文件_config.yml中就有相关的配置。

Problem

当你使用polyfit函数进行多项式拟合之后，你希望计算决定系数或者相关系数看看拟合效果如何。聪明的你肯定觉得聪明的 Matlab 的polyfit函数的返回值中会有\(R^2\)或者\(r\)吧。你尝试disp了一下，发现有一个结构体\(S\)。再查一查帮助文档，发现误差估计结构体\(S\)中只有一个范德蒙德矩阵\(R\)、自由度\(df\)和残差的范数\(normr\)，并没有你想要的\(R^2\)或者\(r\)。

Solution

很遗憾，我们还是需要手动计算这两个系数。

Problem

For a non-negative integer \(K\), we define a level-\(K\) carpet as follows:

• A level-\(0\) carpet is a \(1 \times 1\) grid consisting of a single black cell.
• For \(K>0\), a level-\(K\) carpet is a \(3^K \times 3^K\) grid. When this grid is divided into nine \(3^{K-1} \times 3^{K-1}\) blocks:
  • The central block consists entirely of white cells.
  • The other eight blocks are level-\((K-1)\) carpets.

You are given a non-negative integer \(N\). Print a level-\(N\) carpet according to the specified format.

由于洛谷个人简介迟迟没有维护完毕，故在博客园同步一份

欢迎来看我的博客！

\(\large My Blog\)

\[ \color{purple}\large\textbf{Time is like water flowing eastward,} \] \[ \color{gray}\large\texttt{时间好比东流水} \] \[ \color{red}\large\textbf{only flowing away without flowing back.} \] \[ \color{gray}\large\texttt{只有流去无流回} \]

Codeforces Round 932 (Div. 2) A-D题解

Codeforces Round 932 (Div. 2)

绪言

很菜，AB速度慢，卡在C，想DP，但是时间优化不下来，说服自己\(2\times10^3\)能过\(n^3\)，D稍微简单，但是没看D，遂掉分。

洛谷传送门

调试的有点惨痛的简单字符串模拟题目