Hello to everyone out there. Recently many people on different forums have been asking how to make a recursive function which reverses the string passed to it. But unlike the normal recrusive funtion which only prints out the reversed string, this implementation returns a pointer to reversed string.
Recursive String reversal returning reversed string
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/**
* The actual recursive algo which works behind the scenes
*
* @author ~s.o.s~
* @param src_string The pointer to constant character string which is to be used for reversing
* @param dest_string The pointer to the string which will hold the reversed string
* @return a pointer to the reversed string
*/
char* _string_reverse( const char* src_string, char* dest_string )
{
if( *src_string != '\0' )
{
*dest_string-- = *src_string++ ;
_string_reverse( src_string, dest_string ) ;
}
return dest_string ;
}
/**
* Acts as a simple interface which the main function or any function can call, hides the recursive nature of algo used.
*The creation of the string to be returned occurs in this function which is then used by the recursive alg
*
* @author ~s.o.s~
* @param my_string The const string to be reversed
* @return Returns the reversed string
*/
char* string_reverse( const char* my_string )
{
int length = strlen( my_string ) ;
char* reversed = (char*) malloc( length + 1) ;
reversed[ length ] = '\0' ;
char* tmp = &( reversed[ 0 ] ) ; /// preserve the original pos for returning
reversed = &(reversed[ length - 1 ]) ;
reversed = _string_reverse( my_string, reversed ) ;
return tmp ;
}
/** The driver function which calls the core functionality
* @author ~s.o.s~
*/
int main( void )
{
const char* my_string = "Hello All !!" ;
char* reversed = string_reverse( my_string );
printf( "\n\nOriginal String: %s and Reversed String: {%s}", my_string, reversed ) ;
return 0 ;
}
bumsfeld
413
Nearly a Posting Virtuoso
I can't believe it needs to be that complex!
~s.o.s~
2,560
Failure as a human
Team Colleague
Featured Poster
It is complex since rather than just printing out the reversed string, it "actually" returns a reversed string and that too using recursion.
Have a go at it urself and you will understand its not that simple to handle.
roverphoenix
0
Newbie Poster
actually it looks complex bcoz you have initialized the array in read only memory it would be easier if you had dynamically allocated the array making it r+w
Ancient Dragon
5,243
Achieved Level 70
Team Colleague
Featured Poster
Here is a non-recursive version of the same.
#include <stdio.h>
#include <string.h>
char* _string_reverse( const char* src_string, char* dest_string )
{
char *src_ptr = (char*)src_string + strlen(src_string)-1;
char *dest_ptr = dest_string;
while( src_ptr > src_string)
{
*dest_ptr++ = *src_ptr--;
}
*dest_ptr = 0;
return dest_string;
}
int main()
{
char inbuf[] = "Hello World";
char outbuf[255] = {0};
char *result = _string_reverse(inbuf,outbuf);
printf("%s\n",result);
return 0;
}
~s.o.s~
2,560
Failure as a human
Team Colleague
Featured Poster
actually it looks complex bcoz you have initialized the array in read only memory it would be easier if you had dynamically allocated the array making it r+w
I dont know if I quite get you but are you saying that I should have created the input string dynamically and then modified the same ?
But thats not what I wanted to do, I wanted to keep the input string intact. Also creating two functions -- a interface and one actual functionality helps me get rid of using a static type qualifier.
roverphoenix
0
Newbie Poster
by dynamically I meant doing a malloc and reading from stdin, and I mentioned read only memory since I thought you had used static char * earlier making the string read only, (thts the case with const char * as well), anyhow since thts not what you intended to do thts fine.
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