having a bit of trouble

I'm doing an excercise in a book I bought, but I figured I'd go an extra mile. And i'm having a lot of trouble in getting this to work. Here is what I have (the part that works.)

Code:

---

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

int main(void)
{
        char str[80];
        int i;

        printf("Enter a string: ");
        fgets(str, sizeof(str), stdin);

        for (i = strlen(str); i>-1; i--)
                printf("%c", str[i]);

        printf("\n");
        return 0;

}

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Now, what I want to be able to do, is to store the 'backwards' string in a seperate array, so that I end up with the 'backwards' string in an entirely different array than str. I've tried various loops, but I can't seem to get it to work :/

something like this

Code:

---

char other[80];
...
...
        for (i = strlen (str); i >= 0; i--,x++){
                other[x]=str[i];
                printf ("%c", other[x]);
        }
        x++;
        other[x]='\0';

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Here's one way to do it:

Code:

---

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

int main(void)
{
  char str[80], strrev[80];
  int i;
  int len;

  printf("Enter a string: ");
  fgets(str, sizeof(str), stdin);
  len = strlen(str);
  if(len && str[len-1] == '\n')
    str[--len] = '\0';

  for(i = len-1;i > -1;i--)
    strrev[len-i] = str[i];
  strrev[len+1] = '\0';

  printf("%s\n", strrev);
  return 0;
}

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The reason you need to start at len-1 is because str[len] is the null terminating zero that's at the end of every C string. Reversing the string starting with that character would give you your string reversed, but the null terminating zero would be at strrev[0] so when you printed it you wouldn't see anything. It would literally be a backwards string. I hope that makes sense. I'm guessing that's where you were getting stuck in your own attempts. Let me know if you have any questions about that because it's important to understand.

Quote:

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Reversing the string starting with that character would give you your string reversed, but the null terminating zero would be at strrev[0] so when you printed it you wouldn't see anything.

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That was exactly my problem! Thanks!

I did:

Code:

---

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

int main(void)
{
        char str[80], backwards[80];
        int i,x=0;

        printf("Enter a string: ");
        fgets(str, sizeof(str), stdin);

        for (i = (strlen(str) - 1); i>=0; i--,x++)
        {
                backwards[x]=str[i];
        }

        backwards[x] = '\0';
        printf("%s", backwards);

        return 0;
}

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