String manipulation

smithslist · 24-10-2006 04:32PM #1

hi guys,

I am wondernig can anybody help me, I have an input (String) for example "1122334455FF" and what I am looking to do is to break down down
like:
"11 22 33 44 55 FF", so a space is inserted after every second value.

any help would be great.

thanks.....

Stugots · 24-10-2006 04:55PM

The resulting string is going to be larger than the first string, so you need to figure out the size of the resulting string and allocate enough memory for that. Then its just a simple loop copying the data from the first string to the allocated buffer and inserting a space after every two characters.

seamus · 24-10-2006 05:57PM

Is this an assignment? What language are you using?

Post up some code, or even your own ideas that you've done already. This is a simple problem, so it seems like a college/homework assignment, so you'll need to show that you've done some work on this first.

smithslist · 25-10-2006 08:48AM

sorry guys i forgot to mention it, it is in java and it is something somebody in work asked me and i was confused how to do it.

but got it working....here is the code that after every two single char a space is placed, thus "112233445566" becomes "11 22 33 44 55 66"

String string = "112233445566";
if (string.length() < 3)
{
}
else {
String firstTok = string.substring(0,2);
String leftover = string.substring(2,string.length());
string = firstTok+" "+recursive_thing(leftover);
string = firstTok+" "+recursive_thing(leftover);
}
System.out.println("string "+string);

hope it helps none who needs it

thanks...........

smithslist · 25-10-2006 08:51AM

was told there is a simplier way of doing it, simplier meaning for beginners (in programming) to understand better.......nbody knows a way wuld b good

quite amazed how a simple task wreck my head for so long......

Evil Phil · 25-10-2006 09:11AM

Is the string always going to be of a fixed length? You should try looping through the string if not.

smithslist · 25-10-2006 09:56AM

no its aint a fix string, but I stated to do something like this, the string would have to b even.....so I told her to introduce a try catch exception to check on input if the length is a even length or not.

try
{
string = string.trim();
if (string.length() % 2 != 0)
{
throw new Exception();
}

}
catch (Exception e)
{
MainClass.displayErrorMessage("blah blah " + string);
return;
}

dal · 25-10-2006 10:56AM

public static String insertSpaces (String input)
{
	StringBuffer stringbuffer = new StringBuffer();
	
	int insertSpaceIndex = 2;
	int inputStringLength = input.length();
	
	int i = 0;
	while (i + insertSpaceIndex <= inputStringLength)
	{
		stringbuffer.append(input.substring(i, i + insertSpaceIndex) + " ");
		i = i + insertSpaceIndex;
	}
	
	return stringbuffer.toString();
}

You could use that, though it will append a space on the very last iteration as well, though this is easily avoided.

Civilian_Target · 25-10-2006 01:32PM

How about:

public String addSpaces(String noSpaces)
{
    if(noSpaces.length() > 2)
        return noSpaces.substring(0,2) +" " +addSpaces(noSpaces.substring(2,noSpaces.length()));  
    return noSpaces;
}

Goddamn typo

Webmonkey · 25-10-2006 02:39PM

in java can you not threat a string as a charactor array? well deep down this is what it really is but i never worked with java so don't know.

What i would do this and detect if it is an even number and place a space in if it was. For example in c++

string mystring = "1122334455FF";
int numofextraspaces = mystring.size()/3;

char outputstring[15] = "";
int lastpos;
bool changed =false;

	for (int k = 1; k < mystring.size()+numofextraspaces; k++)
	{
	    
	    if (!changed)
	    	lastpos = k-1;

	    
	     if (k%3==0)
	       {
	       		outputstring[k-1]= '  ';
	       		lastpos = k-1;
	       		changed = true;
	        }
	        
	     else
	        {
	        	outputstring[k-1] = mystring[lastpos];

	        }

	}

Very simple, hope that would work though.

Civilian_Target · 25-10-2006 03:07PM

Surely that's just going to overwrite every evenly numbered character with a space?

Webmonkey · 25-10-2006 03:30PM

well its k, it doing the calculatino on, not the charactor. So its positions its dealing with, not values. But i just noticed that that will do a space at start and every second one after that.

edit: fixed

Mutant_Fruit · 25-10-2006 03:49PM

Nice idea, but what that code does is replace (oerwrite) every third character with a ' '. Not quite what is wanted :P

EDIT: smithslist, it's perfectly ok to ask questions about homework here so long as you show that you've done some work at the problem and can explain what your code *isn't* doing right. But tbh i really doubt the "someone asked me in work" story, unless of course work is teaching you and your friend to learn very basic coding skills using java...

Webmonkey · 25-10-2006 03:51PM

it overwrites it with a space as far as i can see

, but if that causes difficulty i suppose you could cast the ASCII code.

Edit: Ok i see the problem, my mistake

- once again!
You could use a ready made functino or a custom made one to shift all elements right to create holes to insert the spaces i suppose

Right i don't want to even explain this:

string mystring = "1122334455FF";
int numofextraspaces = mystring.size()/3;

char outputstring[15] = "";
int lastpos;
bool changed =false;

	for (int k = 1; k < mystring.size()+numofextraspaces; k++)
	{
	    
	    if (!changed)
	    	lastpos = k-1;

	    
	     if (k%3==0)
	       {
	       		outputstring[k-1]= '  ';
	       		lastpos = k-1;
	       		changed = true;
	        }
	        
	     else
	        {
	        	outputstring[k-1] = mystring[lastpos];

	        }

	}

but it doesn't work properly. See you need a constant to create the charactor array, and unfort you don't know the size of the string until you enter the program. I'm sure there is some smart way of allocating memory dynamically?

I'm giving up, its doesn't include the 44 in the new string. Got assignments to do myself but id spend more time if i could. Might give some ideas

smithslist · 26-10-2006 09:26AM

Mutant_Fruit i dont wanna get into form wars or nthing, but i did programming years ago in coll, even thou it wasnt much but it was basic, and thats why here i post this query and others b4 this to help me (and work pals) out wit queries lik the one above.....

i am learnin to program again in my company, and one of my work pals (only recently joined) hence "someone asked me in work", asked me the q bout it, and i wanted to help her out.......so dat is why

once again, thanks to all who helped me out, much appreciated....thanks

Kev · 26-10-2006 09:55AM

Theres hundreds of ways of doing it, heres one in one line of code

string = string.replaceAll( "(..)", "$1 " );

note: won't work on ancient jdk's

Kev · 26-10-2006 10:07AM

Modification to ensure it doesn't add a space at the end

string = string.replaceAll( "(..)(?!$)", "$1 " );

Blowfish · 26-10-2006 11:15AM

Kev wrote:

string = string.replaceAll( "(..)(?!$)", "$1 " );

^ i'd definitely agree with this one, it's too the point, and the most efficient.

Webmonkey · 26-10-2006 11:16AM

A hell lot easier and quicker than my approach

Mutant_Fruit · 26-10-2006 04:49PM

string start = "aabbccddeeff";
string result = null;
for(int i = 0; i < start.Length; i++)
{
    // If we're not at the start AND we're not at the very end
    // AND we've copied 2 characters since our last space was entered
    if((i != 0) && (i % 2 == 0) && (i != start.length-1))
        result += " ";

    result += start[i];
}

// result should now equal: "aa bb cc dd ee ff"

There are nicer ways of doing it with regex, but that's a simple way of doing it, assuming your chosen language allows string concateration. I'm too lazy to write a C version which does the same thing

Also, i didn't compile or test this, but i assume it works. 10 bonus points if i made a mistake

dal · 26-10-2006 08:13PM

Mutant_Fruit wrote:
string start = "aabbccddeeff";
string result = null;
for(int i = 0; i < start.Length; i++)
{
    // If we're not at the start AND we're not at the very end
    // AND we've copied 2 characters since our last space was entered
    if((i != 0) && (i % 2 == 0) && (i != start.length-1))
        result += " ";

    result += start[i];
}

// result should now equal: "aa bb cc dd ee ff"
There are nicer ways of doing it with regex, but that's a simple way of doing it, assuming your chosen language allows string concateration. I'm too lazy to write a C version which does the same thing Also, i didn't compile or test this, but i assume it works. 10 bonus points if i made a mistake

Being extra pedantic here, but in java its generally bad practice to concatenate in this way as it actually creates a brand new String object every single time (Strings are immutable). Its better to use a Stringbuffer and to append.

Mutant_Fruit · 26-10-2006 10:02PM

I agree 100%

A far better solution would be a StringBuilder, but i wasn't going to complicate the issue

String arithmetic in languages with immutable strings is a bad idea. Then again, if you're only doing 2-4 string "additions" then you're sometimes best not using a StringBuilder. It all depends.

String manipulation

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