Only part of the code executing

chaacoali · 08-08-2012, 09:16 AM

Code:

int main()
{
char str[10],str2[10];
int k,i=0,j;
printf("enter de string\n");
scanf("%s",str);
k=strlen(str);
printf("length of de string %d\n",k);
        for(j=k-1;j=0;j--)
        {
        str2[i++]=str[j];
        }
printf("%s",str2);
        for(i=0;i<k;i++)
        {
            if(strcmp(str,str2)==0)
                {
                printf("palindrome");
                }
        }
return 0;
}

this is my output

Code:

enter de string
jamiaj
length of de string 6

Why is the code after printing the length not working.

pixellany · 08-08-2012, 09:30 AM

Is this legal syntax?

Code:

for(j=k-1;j=0;j--)

maybe try putting a diagnostic printf inside that loop

chaacoali · 08-08-2012, 09:34 AM

why.? what is wrong with this code.? j starts from say 5 n decrements every time.

Nylex · 08-08-2012, 09:35 AM

Quote:

Originally Posted by pixellany

Is this legal syntax?

Code:

for(j=k-1;j=0;j--)

It is. The code wouldn't compile if it wasn't.

I'd probably avoid replying to threads if you're not sure you can help, so you don't remove them from the zero reply list.

chaacoali · 08-08-2012, 09:42 AM

Quote:

Originally Posted by Nylex

It is. The code wouldn't compile if it wasn't.

I'd probably avoid replying to threads if you're not sure you can help, so you don't remove them from the zero reply list.

Can u please tell me what could be wrong.? Breaking my head over this, not able to understand what is wrong.

NevemTeve · 08-08-2012, 09:55 AM

To start:

Code:

old: for(j=k-1;j=0;j--)
new: for(j=k-1;j>=0;j--)

rstewart · 08-08-2012, 10:00 AM

Quote:

why.? what is wrong with this code.? j starts from say 5 n decrements every time.

No it dosen't. You are doing an assignment with your statement of j=0, not a comparison - the loop is NOT being executed. Anyways the correct comparison wouldn't be j==0 either, the comparison that you want to do in your loop is j>=0.

You have other issues with your code as well that you need to look at, but I figured I would point out the first problem and let you figure out the rest.

chaacoali · 08-08-2012, 10:09 AM

Quote:

Originally Posted by NevemTeve

To start:

Code:

old: for(j=k-1;j=0;j--)
new: for(j=k-1;j>=0;j--)

Thanks a lot, silly mistake. The later part of the code is still not working. I edited my code to this

Code:

int main()
{
char str[10],str2[10];
int k,i=0,j;
printf("enter de string\n");
scanf("%s",str);
k=strlen(str);
printf("length of de string %d\n",k);
        for(j=k-1;j>=0;j--)
        {
        str2[i++]=str[j];
        }
printf("%s\n",str2);
printf("length of reversed string %d",strlen(str2));
       if(strcmp(str,str2)==NULL)
            {
                printf("palindrome");
        }
return 0;

This is the output

Code:

enter de string
james
length of de string 5
semaj��
length of reversed string 7

chaacoali · 08-08-2012, 10:14 AM

How did those extra 2 characters(junk ) get added to str2, also I'm getting this error

warning: comparison between pointer and integer in the strcmp fn line

NevemTeve · 08-08-2012, 10:14 AM

Insert this line before/after the cycle: str2[k]= '\0'

PS: strcmp returns a number, not a pointer, so use ==0, not ==NULL

chaacoali · 08-08-2012, 10:23 AM

I replaced NULL with 0 and the warning disappeared but still not getting the desired result

Code:

enter de string
james
length of de string 5
semaj��
length of reversed string 7
not palindrome[root@localhost c]# ./a.out
enter de string
jaiaj
length of de string 5
jaiaj��
length of reversed string 7
not palindrome

NevemTeve · 08-08-2012, 10:26 AM

Insert this line before/after the cycle: str2[k]= '\0'

chaacoali · 08-08-2012, 10:29 AM

Quote:

Originally Posted by NevemTeve

Insert this line before/after the cycle: str2[k]= '\0'

PS: strcmp returns a number, not a pointer, so use ==0, not ==NULL

Thanks a lot. That helped. So everytime I reverse a string or do any string operations of this sort I should make sure I replace the kth character by end of string.

But could you please explain how those junk characters are formed.? I'm only able to figure out the occurence of first junk character which is because of i++ statement. How is it that the other one occurs.?

NevemTeve · 08-08-2012, 11:45 AM

This thing is called memory garbage. What you have to remember is adding a terminating zero to the end of a string you create manually. (Strings created by library functions (strcpy, strcat, sprintf, getenv etc) are already zero-terminated.)

chaacoali · 08-08-2012, 12:10 PM

Quote:

Originally Posted by NevemTeve

This thing is called memory garbage. What you have to remember is adding a terminating zero to the end of a string you create manually. (Strings created by library functions (strcpy, strcat, sprintf, getenv etc) are already zero-terminated.)

I had a similar program but in that case this garbage values didn't appear. So you mean to say its not necessary that it should always happen, but it is possible for such a thing to happen(garbage values).?

So this problem, is it caused because of my str2[i++] statement or is it because of something else.?