I have a following code:
#include <stdio.h>
void recursion(char *ptr) {
if(*ptr!='J') recursion(ptr++);
printf("%c",*ptr);
}
void main() {
char v[]="!zenaJ";
char *ptr=v;
recursion(ptr);
}
I would like to return Janez! trough the recursive function. I don't have any errors when compiling. When I run the program I get an error "Segmentation fault (core dumped)". What am I doing wrong?
You are passing recursively the same pointer
if(*ptr!='J') recursion(ptr++);
because the value of the post-increment expression ptr++ is the value of the pointer before its incrementing.
The function written in C can look the following way
void recursion( const char *ptr )
{
if ( *ptr )
{
recursion( ptr + 1 );
putchar( *ptr );
}
}
In C++ the function can look the following way
std::ostream & recursion( const char *ptr, std::ostream &os = std::cout )
{
if ( *ptr )
{
recursion( ptr + 1 );
os << *ptr;
}
return os;
}
Pay attention to that according to the C Standard the function main without parameters shall be declared like
int main( void )
and in C++ it can be declared like
int main()
The increment of ptr occurs only after the recursive call for recursion.
A simple fix should be:
#include <stdio.h>
void recursion(char *ptr) {
if (*ptr != 'J')
{
char c = *ptr;
ptr++;
recursion(ptr);
printf("%c",c);
}
else
{
printf("%c", 'J');
}
}
void main() {
char v[]="!zenaJ";
char *ptr=v;
recursion(ptr);
}
recursion(ptr++);to do?ptr++and++ptr?"%c%"is invalid. I assume you mean"%c".