Thread: Have a problem with the following code.

Hi all,
I know that there is something wrong with my code, can anyone pls help me to edit my code.
What the code did was to take in a character and produce the reverse of that character.
input --> hello world
output --> dlrow olleh

Code:

#include <stdio.h>

void reverse ();

int
main(void)
{
     char s[100];

     while (fgets(s, 100, stdin) != NULL)
     {
	  printf("%s\n", s);
	  void reverse(int s);
	  printf("String length == %d\n", strlen(s));
     }

     return 0;
}

void reverse(int s)
{ 
     int i;
     for(i=(sizeof(s)-1); i=0; i--)
    {
       printf("reverse string: %s", s);
    }
}

Well, one problem is that you have a function prototype where you're trying to call reverse(). Another problem is that reverse() really wants a string, but you have it set up to receive an int.

Really, doesn't your compiler give you error messages?

why do you want to use "-2" in the "for" loop.

Code:

for ( i = strlen(s) - 2; i >= 0; i-- ) {

I try it with "-1" and it produce the same result...

>why do you want to use "-2" in the "for" loop.
fgets copies the newline as well. - 1 for the null character, - 2 for the null character and the newline.

However, this assumes that there actually is a newline. There's no guarintee that there will be a newline. All I have to do is type 100 characters before hitting enter.

Quzah.

>All I have to do is type 100 characters before hitting enter.
You don't have to work nearly that hard. 99 characters should be enough to break it.

Ya.. got it, thanks everyone......

[code]
#include <stdio.h>
#include <string.h>

void reverse(char []);

int
main(void)
{
char s[100];

while (fgets(s, 100, stdin) != NULL)
{
printf("%s", s);
printf("reverse string:");
reverse(s);
printf("\nString length == %d\n", strlen(s));
}

return 0;
}

void reverse(char s[])
{
int i;
for(i=(strlen(s)-1); i>=0; i--)
{
printf("%c", s[i]);
}
}
[\code]

This code did reverse the character input for it always have a '\n' after each character, is there any way that i can put all the reserved character and print them out all at once.

Now when i compare and run the code, the output i get is

Code:

Enter a string of character: this
String of character entered: this
Reversed string: s
Reversed string: i
Reversed string: h
Reversed string: t
String length == 5

How can i make it this way

Code:

Enter a string of character: this
String of character entered: this
Reversed string: siht

Thanks...

>did any one get this problem when solving the above prob
Only those that wrote the same broken code as you.

>i=sizeof temp
temp is a pointer, so i would most likely be 2 or 4, not the size of str, and most certainly not the size of a variable length string entered by the user. This would work better:

Code:

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

void rev ( char str[] );

int main ( void )
{
  char str[25];

  while ( fgets ( str, sizeof str, stdin ) != NULL )
    rev ( str );

  return 0;
}

void rev ( char str[] )
{
  int i = 0;
  int j = strlen ( str ) - 1;
  char temp[25];

  while ( j >= 0 )
    temp[i++] = str[j--];
  temp[i] = '\0';

  printf ( "%s\n", temp );
}

But since it's trivial to reverse a string in-place, you don't need the error prone temporary array:

Code:

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

void rev ( char str[] );

int main ( void )
{
  char str[25];

  while ( fgets ( str, sizeof str, stdin ) != NULL ) {
    rev ( str );
    printf ( "%s\n", str );
  }

  return 0;
}

void rev ( char str[] )
{
  int i = 0;
  int j = strlen ( str ) - 1;

  while ( i < j ) {
    char save = str[i];
    str[i++] = str[--j];
    str[j] = save;
  }
}

> for(i=sizeof temp
Try strlen(temp)

sizeof() simply tells you the size of a pointer (which is all you get when you pass an array to a function)