Really hard to solve

[giladanon]

we got an question in class today that's stuck on my mind and i can't get it solved anyway i try.
the question was:
you get by input a char between 'a' to 'z'.
how do you return the next char (a->b, f->g) in the alphabetical cycle (not capital) without the use of "if"s...
i broke my brain trying to solve this and with no luck.
any ideas? (:

[Zachm]

The problem you encounter is with the character 'z' right? because with all other chars, you just need to return (char)(c+1).
There might be several solutions, dependent on the programming language.
A "too clever" answer would be to use a switch statement or the ? : trinary operator, but this would be semantically identical to using an "if ... else ..." statement.

I have a hunch you will need to use the modulo operator (%) to solve this one...

Regards,
Zachm

[ProgramArtist]

Hi,

What about this:

char GetTheNextCharWithoutAnyIf(const char cIn)
{
    char chars['z'-'a'+2] = "bcdefghijklmnopqrstuvwxyza";
    return chars[cIn-'a'];
}

?

With regards
Programartist

[laserlight]

What about this: (...)?

It should work, though it uses a little more space than Zachm's hunch and still depends on the letters being contiguous and in alphabetical order in the character set. You could simplify to:

char chars[] = "bcdefghijklmnopqrstuvwxyza";
return chars[cIn - 'a'];

or even:

return "bcdefghijklmnopqrstuvwxyza"[cIn - 'a'];

[HappyNerd]

It should work, though it uses a little more space than Zachm's hunch and still depends on the letters being contiguous and in alphabetical order in the character set. You could simplify to:

char chars[] = "bcdefghijklmnopqrstuvwxyza";
return chars[cIn - 'a'];

or even:

return "bcdefghijklmnopqrstuvwxyza"[cIn - 'a'];

I dont think so mate, else what what will happen if the user types "a"? u changed the arrangement for nothing. programArtist's original code seems good.

[laserlight]

I dont think so mate, else what what will happen if the user types "a"?

'b' will be returned, of course, since 'a' - 'a' == 0. What did you think will happen?

u changed the arrangement for nothing.

I changed the arrangement as a simplification.

programArtist's original code seems good.

It is, except that during review you are forced to check that the expression 'z'-'a'+2 is correct, when you could just let the compiler compute the size for you.

[ProgramArtist]

Hi,

my code is working as laserlight's does too.
He tried to improve the code (and succeeded).
The only intention of my post was to present a solution for the given task from the OP.
With regards
Programartist

[GeoRanger]

I tend to avoid lookup tables. Following up on Zachm's suggestion of using modulo:

return (cIn + 1 - 'a') % ('z' - 'a' + 1) + 'a';

In this case the lookup is probably faster.

[naemi]

We java people have twisted minds, I prefix my solution thus because what I present to you isn't pretty but it does the job and fulfills the requirements... yep...

public class CharGetter {
	public char getTheNextCharWithoutAnyIf(char cIn) throws Exception {
		try {
			return (Character)this.getClass().getMethod("" + cIn, null).invoke(this, null);
		} catch(NoSuchMethodException e) {
			throw new Exception("Big trouble!", e);
		} catch(IllegalAccessException e) {
			throw new Exception("Big big trouble!", e);
		}
	}

	private char a() {
		return 'b';
	}
	private char b() {
		return 'c';
	}
	private char c() {
		return 'd';
	}
	private char d() {
		return 'e';
	}
	private char e() {
		return 'f';
	}
	private char f() {
		return 'g';
	}
	private char g() {
		return 'h';
	}
	private char h() {
		return 'i';
	}
	private char i() {
		return 'j';
	}
	private char j() {
		return 'k';
	}
	private char k() {
		return 'l';
	}
	private char l() {
		return 'm';
	}
	private char m() {
		return 'n';
	}
	private char n() {
		return 'o';
	}
	private char o() {
		return 'p';
	}
	private char p() {
		return 'q';
	}
	private char q() {
		return 'r';
	}
	private char r() {
		return 's';
	}
	private char s() {
		return 't';
	}
	private char t() {
		return 'u';
	}
	private char u() {
		return 'v';
	}
	private char v() {
		return 'w';
	}
	private char w() {
		return 'x';
	}
	private char x() {
		return 'y';
	}
	private char y() {
		return 'z';
	}
	private char z() {
		return 'a';
	}
}

[Zachm]

If we're going for an overkill, there are many funny ways of doing stuff .
For instance, this some what odd way of approximating Pi :

#include <stdio.h>
#define _ F-->00 || F-OO--;
long F=00,OO=00;

void F_OO();

int main()
{
	F_OO();
	printf("%1.3f\n", 4.*-F/OO/OO);
	return 0;
}

void F_OO()
{
            _-_-_-_
       _-_-_-_-_-_-_-_-_
    _-_-_-_-_-_-_-_-_-_-_-_
  _-_-_-_-_-_-_-_-_-_-_-_-_-_
 _-_-_-_-_-_-_-_-_-_-_-_-_-_-_
 _-_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
 _-_-_-_-_-_-_-_-_-_-_-_-_-_-_
 _-_-_-_-_-_-_-_-_-_-_-_-_-_-_
  _-_-_-_-_-_-_-_-_-_-_-_-_-_
    _-_-_-_-_-_-_-_-_-_-_-_
       _-_-_-_-_-_-_-_-_
            _-_-_-_

}

Regards,
Zachm

[naemi]

Yeah, I know, that's Westley's 1988 obfuscated c contest entry, plenty more there for those interested: http://www0.us.ioccc.org/years.html#1988_westley
I think there ought to be an obfuscated java contest though -- there's so much boring java code in the world it's about time someone spiced it up a little. My personal favorite way is to use something like the class below and start having your code compile more code that compiles more code -- pretty soon no one but you has any idea where all the code in your program is coming from (of course the downside is after a while, neither do you...)

public class MyLoader extends ClassLoader {

	/**
	 * Compiles given class, or returns null if unsuccessful.
	 * @param name
	 * @param source
	 * @return
	 * @throws Exception
	 */
	public Class<?> load(String name, String source) throws Exception {
		JavaCompiler jc = ToolProvider.getSystemJavaCompiler();
		StringFileObject sourceFO
				= new StringFileObject(name, source);
		VirtualFileManager fileManager
				= new VirtualFileManager(
				jc.getStandardFileManager(null, null, null));
		JavaCompiler.CompilationTask ct = jc.getTask(
				null, fileManager, null, null, null, Arrays.asList(sourceFO));
		boolean success = ct.call();

		if(success) {
			VirtualFileObject[] files = fileManager.getFiles();
			if(files.length != 1) {
				throw new IllegalStateException(
						"Unexpected number of virtual files created: "
						+ files.length
						+ ", expected: 1.");
			} else {
				byte[] bytes = files[0].getBytes();
				Class<?> result	= load(bytes);
				return result;
			}
		} else {
			return null;
		}
	}

	/**
	 * Loads a class defined by a string of text contained inside
	 * the bytes array.
	 * 
	 * @param bytes
	 * @return
	 */
	public Class<?> load(byte[] bytes) {
		return super.defineClass(null, bytes, 0, bytes.length);
	}
}