path: root/sduacm2017/lec2/lec.tex

\documentclass[aspectratio=169,hyperref={pdfencoding=auto,psdextra}]{beamer}
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\usepackage{graphicx}
\usepackage{fancyvrb}
\usepackage{amsmath}
\usepackage{multicol}
\usetheme{Malmoe}
\usecolortheme{default}
\begin{CJK*}{UTF8}{gbsn}
\title{「有了他我们无法活」}
\subtitle{——炮打司令部}
\author{Chris Xiong}
\date{2017-07-28}
\begin{document}
	\frame{\titlepage}
	\begin{frame}
		\frametitle{「有了他我们无法活」}
		\framesubtitle{Outline}
		\begin{itemize}
			\item 采访
			\item Faster I/O
			\item C++11 / 14
			\item Common pitfalls
			\item Bitmask
			\item Bitmask+dp
			\item 如何让队友认错之如何表扬队友
		\end{itemize}
	\end{frame}
	\begin{frame}
		\frametitle{采访}
		\framesubtitle{\sout{a.k.a. 教学质量检查}}
		\begin{itemize}
			\item 上次课讲的内容大家都听懂了吗？\pause
			\item 什么？不懂？\pause
			\item 那还记得上次讲的什么吗？\pause
			\item 对不起，这次没有A Water Problem
		\end{itemize}
	\end{frame}
	\begin{frame}[fragile]
		\frametitle{Faster I/O}
		Why?
		\begin{itemize}
			\item No need to parse the format string
			\item Makes better use of the I/O buffer
		\end{itemize}
		\pause
		How?
		\begin{itemize}
			\item \verb|.sync_with_stdio(false)|
			\item \verb|getchar()|
			\item \verb|fread()|
		\end{itemize}
\end{frame}
	\begin{frame}[fragile]
		\frametitle{Faster I/O}
		\framesubtitle{Faster input - getchar()}
		\begin{Verbatim}
		int readint()
		{
			int ret=0;
			char ch=getchar();
			while(ch<'0'||ch>'9')
				ch=getchar();
			do
			{
				ret=ret*10+ch-'0';
				ch=getchar();
			}while(ch>='0'&&ch<='9');
			return ret;
		}
		\end{Verbatim}
\end{frame}
	\begin{frame}[fragile]
		\frametitle{Faster I/O}
		\framesubtitle{Even faster input - fread()}
		\begin{Verbatim}
		char s[SOME_LARGE_VALUE];
		size_t ptr,len;
		len=fread(s,1,SOME_LARGE_VALUE,stdin);
		int readint()
		{
			//replace getchar() with s[ptr++]
			...
		}
		\end{Verbatim}
		\pause
		Reading real numbers?
\end{frame}
	\begin{frame}[fragile]
		\frametitle{Faster I/O}
		\framesubtitle{Faster output}
		\begin{itemize}
			\item Print digit by digit
			\item Save to buffer then \verb|fwrite()| to \verb|stdout|.
		\end{itemize}
\end{frame}
	\begin{frame}[fragile]
		\frametitle{C++11 / 14 - Useful features that reduces coding efforts}
		\framesubtitle{C++11}
		\begin{itemize}
			\item Uniform initialization
			\begin{Verbatim}
	struct S{int a;double b;char c;};
	S s{1,2.0,'3'};//s.a==1; s.b==2.0; s.c=='3';
			\end{Verbatim}
			\item Type inference
			\begin{Verbatim}
	std::set<int> s;
	auto a=1;
	auto it=s.begin();
			\end{Verbatim}
			\item Range-based for loop
			\begin{Verbatim}
	std::vector<int> v;
	for(auto &i:v)...
			\end{Verbatim}
		\end{itemize}
\end{frame}
	\begin{frame}[fragile]
		\frametitle{C++11 / 14 - Useful features that reduces coding efforts}
		\framesubtitle{C++11 cont'd}
		\begin{itemize}
			\item Lambda functions
			\begin{Verbatim}
std::sort(p+1,p+nv,[o=p[0]](const v3d& a,const v3d& b)->bool
	{
		double cross=(a.x-o.x)*(b.y-o.y)-(b.x-o.x)*(a.y-o.y);
		if(sgn(cross))return sgn(cross)>0;
		double la=hypot(a.x-o.x,a.y-o.y);
		double lb=hypot(b.x-o.x,b.y-o.y);
		return la<lb;
	}
);
			\end{Verbatim}
			\item Right angle bracket
			\begin{Verbatim}
	std::vector<std::pair<int,int>> v;
			\end{Verbatim}
			\item \verb|long long int|\\
			Yeah, it was not standard until C++11 (C99).
		\end{itemize}
\end{frame}
	\begin{frame}[fragile]
		\frametitle{C++11 / 14 - Useful features that reduces coding efforts}
		\framesubtitle{C++11 STL}
		\begin{itemize}
			\item Hash tables\\
			\verb|std::unordered_map, std::unordered_set|
			\item \verb|std::tuple|
			\item Regular expressions
			\item Threading
			\item Random number generators
		\end{itemize}
\end{frame}
	\begin{frame}[fragile]
		\frametitle{C++11 / 14 - Useful features that reduces coding efforts}
		\framesubtitle{C++14}
		C++14 is a small extension to C++11.
		\begin{itemize}
			\item Improved \verb|auto|
			\begin{Verbatim}
	auto factorial(int x){
		if(x==1)return 1;
		return x*factorial(x-1);
	}
			\end{Verbatim}
			\item Improved lambda functions
			\begin{Verbatim}
	auto lambda=[](auto x,auto y){return x+y;};
			\end{Verbatim}
			\item Lambda capture expressions
		\end{itemize}
\end{frame}
	\begin{frame}[fragile]
		\frametitle{Common pitfalls}
		\begin{itemize}
			\item Huge global variable causes linkage error.
			\begin{Verbatim}
int a[1LL<<12][1LL<<48],b[1LL<<12][1LL<<48],c[1LL<<12][1LL<<48];
int main(){c[0][0]=1;}
			\end{Verbatim}
			Compilation result:
			\begin{Verbatim}
g++ -Wall -std=c++14 -g -o "test" "test.cpp" -lm (in directory:
/home/chrisoft/code)
/tmp/ccOkFQ7A.o: In function `main':
/home/chrisoft/code/test.cpp:2:(.text+0x6):
relocation truncated to fit: R_X86_64_PC32 against symbol
`c' defined in .bss section in /tmp/ccOkFQ7A.o
collect2: error: ld returned 1 exit status
Compilation failed.

			\end{Verbatim}
			\item relocation of \verb|.bss| section exceeding platform limitations.
		\end{itemize}
\end{frame}
	\begin{frame}[fragile]
		\frametitle{Common pitfalls}
		\begin{itemize}
			\item Stack size is very small compared to heap
			\begin{Verbatim}
int main(){int a[100000000];...}
			\end{Verbatim}
			\item Results in stack overflow.
			\item Math library
			\item \verb|memset()| TLE
		\end{itemize}
\end{frame}
	\begin{frame}
		\frametitle{Bitmask}
		\begin{itemize}
			\item A set in its binary form
			\item Codeforces 550B\pause
			\item Codeforces 579A
		\end{itemize}
	\end{frame}
	\begin{frame}
		\frametitle{Bitmask+dp}
		\begin{itemize}
			\item Concept of a \textbf{state}\pause
			\item Value function\pause
			\item Initial state
		\end{itemize}
	\end{frame}
	\begin{frame}
		\frametitle{Bitmask+dp}
		\begin{itemize}
			\item TSP(Travelling Salesman Problem)
			\item Given a list of cities and the distances between each pair of cities,
			what is the shortest possible route that visits each city exactly once and
			returns to the origin city?\pause
			\item f[s][i]: s: set of visited cites, i: current city
			\item functional equation:
				$
					f[s][i]=
					\displaystyle \min_{k:N}f[s-{i}][k]+dist[k][i] (k\notin s)
				$
			\item Initial state: f[U][0]=0;\pause
			\item Variant\pause
			\item Loop direction
		\end{itemize}
	\end{frame}
	\begin{frame}
		\frametitle{Bitmask+dp}
		\begin{itemize}
			\item TSP: POJ 3311
			\item Counting: POJ 3254
			\item f[i][s]: row i with set s occupied
		\end{itemize}
	\end{frame}
	\begin{frame}
		\frametitle{如何让队友认错之如何表扬队友}
		\framesubtitle{队友需要表扬才能更有生产力}
		\includegraphics[scale=0.75]{zz1.png}
	\end{frame}
	\begin{frame}
		\frametitle{如何让队友认错之如何表扬队友}
		\framesubtitle{光辉事迹}
		\begin{itemize}
			\item 比赛中要其他队伍帮忙写对拍
			\item 比赛中睡3小时觉
			\item 全权负责实验室事务
			\item 发说说
		\end{itemize}
	\end{frame}
	\begin{frame}
		\frametitle{宇宙智障的说说}
		
		\begin{multicols}{2}
		就终于考完试了\_(:зゝ∠)\_\\
		然而暑假这种？不存在的(滑稽\\
		还是献给辣鸡的(划掉)acm好了\\
		学期结束,事儿反而就又突然多了起来\\
		假装已有计划的专题训练\\
		各种姿势被虐的多校联合\\
		以及暑期集训的萌新教学\\
		与开始正式接手的实验室各种大小事务的锅\\
		相信,一定会是个忙碌的七八月份吧\\
		希望,也同会是个充满收获的七八月\\
		就也会更期待着\\
		在八月初的短假里\\
		与小姐姐愉快的玩耍呢\\
		总之,一定会是个不平凡的假期\\
		再以及,小姐姐寄的明信片也终于到了:)\\
		\end{multicols}
	\end{frame}
	
	\begin{frame}
		\frametitle{宇宙智障的说说}
		\includegraphics[scale=0.5]{zz2.png}
	\end{frame}
	\begin{frame}
		\frametitle{为何要表扬队友}
		\begin{itemize}
			\item 让恬不知耻的队友知道错（似乎对宇宙智障无效）
			\item 叫醒队友
			\item \sout{鼓励}队友\sout{WA更多题}
		\end{itemize}
	\end{frame}
	\begin{frame}
		\frametitle{放假事宜}
		\begin{itemize}
			\item 宇宙智障已经畏罪潜逃
			\item 宇宙智障8月7日将被扭送
			\item 大家一定不用比宇宙智障回来的早
		\end{itemize}
	\end{frame}
\end{CJK*}
\end{document}