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Currently, I am attempting to repeat a single character in the least characters possible. as an example, I am actually using something similar to this to repeat a series of spaces:

printf("%*s",i,"");

And I was wondering if there was a similar, or even shorter/different way in C to repeat a string and print it out, as with the spaces.

I would like something similar to this if possible:

printf("%*s",i,"_");

However, as far as I know, that's not possible, however ideal it would be for me.

To clarify, in these examples the argument i represents the number of times I would like the character to repeat, i.e, the second example should output (if i was say, 12):

____________

NB: It does not necessarily have to be anything related to printf, however, it does have to be short.

Essentially, I would like to repeat one character a specified number of times and then output it.

Edit: I am currently using a for loops which allows me 31 characters, however by using a method similar to the above, I can cut down another 7 characters on top of that, due to the way the program is structured. So a loop is not really ideal.

Bernie
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    Write your own function: `repchar(i, '_');` *you can even call it ... hmmm ... w* `w(42, '_');` – pmg Feb 22 '13 at 09:38
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    i'm not sure if i got it correctly, but why you don't simply do it in a loop? – Hayri Uğur Koltuk Feb 22 '13 at 09:38
  • what do you mean with "shortest number of characters" if you mean that the printf syntax is too verbose then why don't you write your own function with a loop? – AndersK Feb 22 '13 at 09:42
  • @claptrap wouldn't the function definition count to the number of characters? – Scroog1 Feb 22 '13 at 09:44
  • The point is more to get it in the least number of characters, with a loop, which I am currently using, the actual example I can do in about 31 characters, however doing something similar to the above methods would allow me to cut out another 7 chars. I probably should have mentioned this, so I shall edit the thread. – Bernie Feb 22 '13 at 09:45
  • Have you tried looking at http://codegolf.stackexchange.com ? – Scroog1 Feb 22 '13 at 09:49
  • Possible duplicate of [How to repeat a char using printf?](http://stackoverflow.com/questions/14678948/how-to-repeat-a-char-using-printf) – Ciro Santilli OurBigBook.com Mar 24 '17 at 09:33

3 Answers3

2

You can use memset :

void * memset ( void * ptr, int value, size_t num );
// Fill block of memory
// Sets the first num bytes of the block of memory pointed by ptr to the specified value
// (interpreted as an unsigned char).

So you would do, assuming dest is your destination string :

memset(dest, '_', 12);

EDIT : This is a very "raw" solution. It does not put a '\0' at the end of the string, so you have to deal with that too if you want your string only to contain the repeated character and to be formatted the standard way. You of course have to deal with the fact that 12 might be bigger than the space allocated to dest, too.

One last thing : the use of memset is probably more efficient than anything you can do with using your own loops as memset could be implemented in a very efficient way by your compiler (i.e., highly-optimized assembly code).

Fabien
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  • This doesn't terminate `dest` properly though, so that has to happen on the side (meaning more code). – unwind Feb 22 '13 at 09:44
  • Turns out as 3 chars less than my loop. What's the most effective way of defining the dest? – Bernie Feb 22 '13 at 10:03
  • @unwind, sure, I supposed that was only part of the treatment ; I didn't check if the given n# of copies was correct, either. I'll precise that in my answer. – Fabien Feb 22 '13 at 10:11
1

If you don't need the value of i afterwards, either:

for(;i--;printf("x"));

or

while(i--)printf("x");

do it in 22 chars. If you do need i afterwards, and you've got a spare variable j lying around, the shortest using-a-loop I've found uses 25 characters:

for(j=i;j--;printf("x"));

Using a function the best I can do is 28 chars for the function + 5 per call:

r(x){x&&printf("x")&r(--x);}
int main()
{
     int i=12;
     r(i);
}
TripeHound
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0

Super dirty trick if you're interested in one specific char 

#include <stdio.h>

const char *very_long_single_char_string = "___________________________________";

int main()
{
    int i = 4;

    printf("%.*s",i, very_long_single_char_string);

}

Result:

____
Davide Berra
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