[Problem] String repeat(String s, int n) that creates and returns a new string

[tarunjain07]

Hi eveyone

Question is :-

String repeat(String s, int n) that creates and returns a new string that is made by concatenating
n copies of the parameter string s. For example, calling this method with the parameters “Hello”
and 3 would return the string “HelloHelloHello”. If n equals zero, the method should return the
empty string.

I am a beginner in c and trying my hand at recursion .This code doesn't work.
Please guide me and also tell any clever/advance/optimise steps that i can use to code as a pro.

#include<stdio.h>
#include<conio.h>
#include<string.h>


char* Repeat(char *s,int n)
{
char *c;
char *e;
	
  if(n==0)
 {
	return " ";

 }
 
if(n==1)
 {
 	c=strcpy(c,s);
  	return c;
 }

  if(n>1)
 {

  e=Repeat(s,n-1);

  e=strcat(e,s);
  return e;
 }

}




void main()
{
	 char a[]="Hello";
	 char *b;
	 int n;
	 printf("Enter the no of times u want to repeat\n");
	 scanf("%d",&n);
	 b= Repeat(a,n);
	 printf("%s",b);
   
    
    getch();
    
}

[tabstop]

Why do you have c, and e just appearing like magic? You need some variables, and probably more importantly, you need some space to put these strings. Do you know malloc? Now might be a good time to learn.

[CommonTater]

1) Go into your compiler settings and turn the warning levels all the way up.
2) When you compile your code, treat each and every warning as an error to be corrected.

You'll be surprised how smart your compiler is about helping you write decent code.

For example... your variable e ... you just make that up, never declare it, don't initialize it and simply start using it... Your compiler should be complaining about that...

[tarunjain07]

Why do you have c, and e just appearing like magic? You need some variables, and probably more importantly, you need some space to put these strings. Do you know malloc? Now might be a good time to learn.

yes i know malloc
but not getting the use here...
could please edit the function ...i will try to learn/understand by that code...

[tarunjain07]

1) Go into your compiler settings and turn the warning levels all the way up.
2) When you compile your code, treat each and every warning as an error to be corrected.

You'll be surprised how smart your compiler is about helping you write decent code.

For example... your variable e ... you just make that up, never declare it, don't initialize it and simply start using it... Your compiler should be complaining about that...

I am using dev c++ can u tell me for that where and how to ?
and also please tell some compiler for win 7

[AndrewHunter]

I am using dev c++ can u tell me for that where and how to ?
and also please tell some compiler for win 7

You really need to get a new compiler. Take a look at One of the many compiler threads. <------Click there

[anduril462]

Nope, we can not edit the function. You have to do the learning and the coding. We just give you a nudge in the right direction when you're stuck. Here are a few pointers for you:

1. Work the problem out with paper and pencil first, and run through several examples by hand.
2. Count the characters in "Hello" (remember the null), then count the characters in "HelloHelloHello" (remember the null again). Try some other tests. What is the relationship between their lengths? That will tell you how to take your original string, and n, and malloc the right number of bytes for your new string.
3. Translate that into code, little by little, testing as you go. Perhaps start with an iterative (loop) solution, then make it recursive.
4. If you're still stuck, come back and post what you tried.

[CommonTater]

I am using dev c++ can u tell me for that where and how to ?
and also please tell some compiler for win 7

First... if you want to know something about a specific IDE... that's what help files are for.

Dev C++ has been abandoned for quite some time. It's compiler is very out of date and you should look to udating to something current. For C-99 I generally recommend Pelles C <--- click the link!

[CommonTater]

yes i know malloc
but not getting the use here...
could please edit the function ...i will try to learn/understand by that code...

Before you even start trying to use malloc, you need to review your C textbooks/tutorials for the correct way to declare and use variables. You cannot simply make them up as you go!

[tarunjain07]

Before you even start trying to use malloc, you need to review your C textbooks/tutorials for the correct way to declare and use variables. You cannot simply make them up as you go!

ok i will try and willl post back

[tarunjain07]

Before you even start trying to use malloc, you need to review your C textbooks/tutorials for the correct way to declare and use variables. You cannot simply make them up as you go!

i know malloc ..as i have read my textbooks and topics like link list and tree etc..now as i felt that my programming is very weak..
so i am working on this
block by block ..started with recursion ..

[CommonTater]

ok i will try and willl post back

Looking at your edited code I see you are declaring your strings as char* ... nope, not going to work. A pointer is useless without space to store the data in...

AND you are attempting to return a string from your function... Be very careful with this, it doesn't do what you seem to think it does...

FWIW... please don't back edit like that... post a fresh copy, leave the original post alone. Others reading the thread will see the edited code and the conversation following won't make any sense to them at all.

i know malloc ..as i have read my textbooks and topics like link list and tree etc..now as i felt that my programming is very weak..
so i am working on this
block by block ..started with recursion ..

Simply reading the textbook isn't the way to learn C... Work through it page by page, do all the exercises and quizzes, play with the code (it's just as important that you learn what does not work), repeat as necessary, then move on to the next section. When simply reading most people's retention of information (called "comprehension") runs about 60%... if you take the time and work with the code as you learn you can probably drive that up to about 90%... There is a very real difference between "knowing" and "understanding"....

[tarunjain07]

Looking at your edited code I see you are declaring your strings as char* ... nope, not going to work. A pointer is useless without space to store the data in...

AND you are attempting to return a string from your function... Be very careful with this, it doesn't do what you seem to think it does...

FWIW... please don't back edit like that... post a fresh copy, leave the original post alone. Others reading the thread will see the edited code and the conversation following won't make any sense to them at all.

ok..i got what u mean to say...i have to allocate memory by malloc and then return that to char * for storage...
i know thats really foolish of me but i am new

[tarunjain07]

Real men never define acronyms; they understand them genetically - How to write unmaintainable code

it redirects to a site..
boss how to use this site as this has quotes and other stuff

[AndrewHunter]

it redirects to a site..
boss how to use this site as this has quotes and other stuff

That is just part of my signature/tag line. It is not directed towards you.