最近做SPOJ，发现很多题目的读入都是有大幅度优化余地的。事实上，在C++中，使用scanf()读入整数或者实数的速度都非常慢。我们可以通过一次读入一整行的来加快速度，方法是使用gets()。
对于gets()这个函数，GCC的文档建议不要使用。我个人的感觉是只要使用得当，这个函数还是大有用处的。比如下面的代码：
char buf[10000],*o;
inline int getint() {
while (!isdigit(*o) && *o!='-') ++o;
int r = 0,f = *o=='-'?++o,1:0;
while (isdigit(*o)) r = r*10+*o++-'0';
return (f?-r:r);
}
这个代码提供了一个getint()的函数来加快读入整数的速度。我们使用o = gets(buf)，时候就可以进行相关的操作了。在这个函数的基础上稍作改进还可以读入实数等等。
(*O/*_/
Cu #%* )pop mark/CuG 4 def/# 2 def%%%%@@P[TX---P\P_SXPY!Ex(mx2ex("SX!Ex4P)Ex=
CuG #%* *+Ex=
CuG #%*------------------------------------------------------------------*+Ex=
CuG #%* POLYGLOT - a program in seven languages 15 February 1991 *+Ex=
CuG #%* *+Ex=
CuG #%* Written by Kevin Bungard, Peter Lisle, and Chris Tham *+Ex=
CuG #%* *+Ex=
CuG #%* We have successfully run this program using the following: *+Ex=
CuG #%* ANSI COBOL: MicroFocus COBOL85 (not COBOL74) *+Ex=
CuG #%* ISO Pascal: Turbo Pascal (DOS & Mac), Unix PC, *+Ex=
CuG #%* AIX VS Pascal *+Ex=
CuG #%* ANSI Fortran: Unix f77, AIX VS Fortran *+Ex=
CuG #%* ANSI C (lint free): Microsoft C, Unix CC, GCC, Turbo C++, *+Ex=
CuG #%* Think C (Mac) *+Ex=
CuG #%* PostScript: GoScript, HP/Adobe cartridge, *+Ex=
CuG #%* Apple LaserWriter *+Ex=
CuG #%* Shell script: gnu bash, sh (SysV, BSD, MKS), ksh *+Ex=
CuG #%* 8086 machine language: MS-DOS 2.00, 3.03, 4.01, 5.00 beta *+Ex=
CuG #%* VPix & DOS Merge (under unix) *+Ex=
CuG #%* SoftPC (on a Mac), MKS shell *+Ex=
CuG #%* *+Ex=
CuG #%* Usage: *+Ex=
CuG #%* 1. Rename this file to polyglot.[cob|pas|f77|c|ps|sh|com] *+Ex=
CuG #%* 2. Compile and/or run with appropriate compiler and *+Ex=
CuG #%* operating system *+Ex=
CuG #%* *+Ex=
CuG #%* Notes: *+Ex=
CuG #%* 1. We have attempted to use only standard language features. *+Ex=
CuG #%* Without the -traditional flag gcc will issue a warning. *+Ex=
CuG #%* *+Ex=
CuG #%* 2. This text is a comment block in all seven languages. *+Ex=
CuG #%* *+Ex=
CuG #%* 3. When run as a .COM file with MS-DOS it makes certain *+Ex=
CuG #%* (not unreasonable) assumptions about the contents of *+Ex=
CuG #%* the registers. *+Ex=
CuG #%* *+Ex=
CuG #%* 4. When transfering From Unix to DOS make sure that a LF *+Ex=
CuG #%* is correctly translated into a CR/LF. *+Ex=
CuG #%* *+Ex=
CuG #%* Please mail any comments, corrections or additions to *+Ex=
CuG #%* peril@extro.ucc.su.oz.au *+Ex=
CuG #%* *+Ex=
CuG #%*------------------------------------------------------------------*QuZ=
CuG #%* *+Ex=
CuG #%*!Mx)ExQX4ZPZ4SP5n#5X!)Ex+ExPQXH,B+ExP[-9Z-9Z)GA(W@'UTTER_XYZZY'CPK*+
CuG #(* *(
C # */); /*(
C # *) program polyglot (output); (*+
C # identification division.
C # program-id. polyglot.
C #
C # data division.
C # procedure division.
C #
C # * ))cleartomark /Bookman-Demi findfont 36 scalefont setfont (
C # * (
C #
C # * hello polyglots$
C # main.
C # perform
C * ) 2>_$$; echo "hello polyglots"; rm _$$; exit
print
C stop run.
-*, 'hello polyglots'
C
C print.
C display "hello polyglots". (
C */ int i; /*
C */ main () { /*
C */ i=printf ("hello polyglots\n"); O= &i; return *O; /*
C *) (*
C *) begin (*
C *) writeln ('hello polyglots'); (*
C *) (* )
C * ) pop 60 360 (
C * ) pop moveto (hello polyglots) show (
C * ) pop showpage ((
C *)
end .(* )
C)pop% program polyglot. *){*/}比如，下面这几个可以输出自己的程序：
class S{public static void main(String[]a){String s="class S{public static void main(String[]a){String s=;char c=34;System.out.println(s.substring(0,52)+c+s+c+s.substring(52));}}";char c=34;System.out.println(s.substring(0,52)+c+s+c+s.substring(52));}}
char*s="char*s=%c%s%c;main(){printf(s,34,s,34);}";main(){printf(s,34,s,34);}
#define q(k)main(){return!puts(#k"\nq("#k")");}
q(#define q(k)main(){return!puts(#k"\nq("#k")");})
还有用gcc编译输出C，g++编译输出C++的程序：
#include <stdio.h>
int main() {
putchar('C');
#ifdef __cplusplus
putchar('+'); putchar('+');
#endif
return 0;
}
下面的程序输出一个雪花曲线，看起来很像Java，但是却是C：
/*
* Sun's Java is often touted as being "portable", even though my code won't
* suddenly become uber-portable if it's in Java. Truth is, Java's one of
* the most ugly, slow, and straitjacketed languages ever. It's popular
* mainly because people hear the word "portable" and go "ewww".
*
* This program, then, is dedicated to bringing about the death of Java. We
* good coders have been oppressed for too long by the lame language
* decisions of pointy-haired bosses and academics who should know better.
* It's time we stand up against this junk, and bring back the fun in
* programming! Viva La Revolution!
*/
#define aSet c
#define BufferedReader(x)1
#define byte Y[I][_^1]?do(:):_&1?do(.):do(`):8;++y;}
#define class int N=0,_,O=328,l=192,y=4,Y[80][64]={0},I;struct
#define do(c)a(#c "\b")
#define err c,c
#define getAllStrings(x));q()
#define if(x)b(#x)
#define IOException
#define line c
#define main(a)b(char*x){write(1,"\033[",2),null}main()
#define new
#define null a(x);}a(char*x){write(1,x,strlen(x));try;try;try;try;
#define out c,c
#define println(x)c
#define private int d(int
#define public short c;}c;typedef int BufferedReader;char*F="JF>:>FB;;BII";
#define return {return
#define static f(x){N=(N+x)%6,y--?f(0),f(1),f(4),f(1):++Y[(I=O+N[F]-66)
#define String
#define System c
#define this if(D):1,O=I,I/=16,l<_/32?if(B):l>_/32?if(A):2,l=_,_/=16,byte
#define throws
#define toArray(x)c
#define try for(;--c.c;)
#define void /16][(_=l+N[6+F]-66)/16]?O/=16,l/=32,O<I/16?if(C):O>I/16?this
#define while(k)if(2J),if(7;21H),f(0),f(4),f(4),if(H),/*
import java.io.*;
import java.util.*;
/**
* A lame Java program.
* @author J. Random Worker
*/
class LameJavaApp
{
/** The infamous Long-Winded Signature From Hell. */
public static void main(String[] args)
throws IOException
{
/* Don't get me started on this. */
BufferedReader reader =
new BufferedReader(new FileReader(args[0]));
/* What, this long incantation just to print a string? */
System.err.println("Hello world!");
/* At least this is sane. */
String line;
while ((line = reader.readLine()) != null)
System.out.println(line.length());
}
/**
* Method with a needlessly long name.
* @param aSet a set (!)
*/
private String[] getAllStrings(Set<String> aSet)
{
/*
* This dance is needed even in J2SE 5, which has type
* templates. It was worse before that.
*/
return aSet.toArray(new String[0]);
}
}