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Deleting Characters Function

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aznballerlee aznballerlee is offline

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Deleting Characters Function

Nov 23rd, 2006

My task is this, and I'm having trouble finishing up the code:

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Write a function named deleteS that accepts one character pointer as a parameter and returns no value. The parameter is a C string. This function must remove all of the upper and lower case 's' letters from the string. The resulting string must be a valid C string.
Your function must declare no more than one local variable in addition to the parameter; that additional variable must be of a pointer type. Your function may not use any square brackets.
int main()
{
char msg[50] = "She'll be a massless princess."
deleteS(msg);
cout << msg; // prints he'll be a male prince.
}

Here is what I've managed so far:

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
void deleteS (char* ptr[])
{
   int*counter;
   for (counter = ptr; counter<ptr + strlen(ptr); counter++)
   {
       if (isupper(*ptr + counter)
          strcpy (" ", i);
       else if (*(ptr + counter) == 's')
               // delete the s, and move any blankspace back
void deleteS (char* ptr[])
{
   int*counter;
   for (counter = ptr; counter<ptr + strlen(ptr); counter++)
   {
       if (isupper(*ptr + counter)
          strcpy (" ", i);
       else if (*(ptr + counter) == 's')
               // delete the s, and move any blankspace back

I can't seem to come up with the remaining code. I hear that I can use a vector to delete elements (which is what I want to do), but I haven't learned that yet ..

How would I be able to finish up?

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iamthwee

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Re: Deleting Characters Function

Nov 23rd, 2006

http://www.daniweb.com/code/snippet262.html

Bit of an over kill but it works if you convert the line to lower case first.

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 C Syntax (Toggle Plain Text) 
int main(void)
{
   const char before[] = "She'll be a massless princess.";
   printf("before = \"%s\"\n", before);
   test(before, "s", "");
   getchar();
   return 0;
}
int main(void)
{
   const char before[] = "She'll be a massless princess.";
   printf("before = \"%s\"\n", before);
   test(before, "s", "");
   getchar();
   return 0;
}

Last edited by iamthwee; Nov 23rd, 2006 at 4:13 pm.

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Re: Deleting Characters Function

Nov 23rd, 2006

The problem is that I can only use one local variable, and not the entire code you provided for me (thouugh that could work)

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Re: Deleting Characters Function

Nov 23rd, 2006

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Originally Posted by aznballerlee

The problem is that I can only use one local variable, and not the entire code you provided for me (thouugh that could work)

Yup I agree, that is an overkill. If your function doesn't have to return anything, i.e doesn't have to alter the string, I can see how this would be very easy.

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Re: Deleting Characters Function

Nov 23rd, 2006

How would it be easy?? I wish for feedback, as this section of the code is due in hours!

Last edited by aznballerlee; Nov 23rd, 2006 at 4:27 pm.

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Re: Deleting Characters Function

Nov 23rd, 2006

How about using strcat?

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Re: Deleting Characters Function

Nov 23rd, 2006

I see the idea behind strcat now.
I can show you an idea of what I have ..
it compiles but gives no output ..

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
#include <iostream>
using namespace std;
 
void deleteS (char ptr[])
{
    char *counter = ptr;
    for (counter = ptr; counter < ptr + strlen(ptr); counter++)
    {
        if ((*(counter)== 'S') || (*(counter) == 's'))
            continue;
        else
        {    
            strcat(ptr, counter);
            ptr++;
        }
    }
    return;
}
 
int main()
{
    char msg[50] = "She'll be a massless princess.";
    deleteS(msg);
    cout << msg;  // prints   he'll be a male prince.
}
#include <iostream>
using namespace std;

void deleteS (char ptr[])
{
    char *counter = ptr;
    for (counter = ptr; counter < ptr + strlen(ptr); counter++)
    {
        if ((*(counter)== 'S') || (*(counter) == 's'))
            continue;
        else
        {    
            strcat(ptr, counter);
            ptr++;
        }
    }
    return;
}

int main()
{
    char msg[50] = "She'll be a massless princess.";
    deleteS(msg);
    cout << msg;  // prints   he'll be a male prince.
}

Last edited by aznballerlee; Nov 23rd, 2006 at 6:57 pm.

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Re: Deleting Characters Function

Nov 24th, 2006

Both counter and ptr point to the same memory space.. so when you modify ptr in the loop you end up modifying what counter points to.

And btw have you read the description of strcat( ) since it is not doing things in your case whch you are expecting it to do.

You can look into memmove to solve your problem.

Last edited by ~s.o.s~; Nov 24th, 2006 at 2:09 am.

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Re: Deleting Characters Function

Nov 24th, 2006

•

Originally Posted by aznballerlee

My task is this, and I'm having trouble finishing up the code:
Here is what I've managed so far:
Help with Code Tags

C Syntax (Toggle Plain Text)
void deleteS (char* ptr[])
{
   int*counter;
   for (counter = ptr; counter<ptr + strlen(ptr); counter++)
   {
       if (isupper(*ptr + counter)
          strcpy (" ", i);
       else if (*(ptr + counter) == 's')
               // delete the s, and move any blankspace back
void deleteS (char* ptr[]) { int*counter; for (counter = ptr; counter<ptr + strlen(ptr); counter++) { if (isupper(*ptr + counter) strcpy (" ", i); else if (*(ptr + counter) == 's') // delete the s, and move any blankspace back
I can't seem to come up with the remaining code. I hear that I can use a vector to delete elements (which is what I want to do), but I haven't learned that yet ..

How would I be able to finish up?

First thing, your function definition should be void deleteS (char* ptr) -- this passes in a pointer, you are passing in an array of pointers.

Next, set up another character pointer. You are not dealing with integers in this function. I'll call this pointer source

Set this new pointer equal to the parameter, like you did in the for statement. Now both pointers point to the same address.

Start a while loop that exits when when you reach the end of source (*source == '\0')

In the loop,
1) Copy the current character from source to the current character of ptr.
2) Increment source to point to the next character.
3) If the current character in ptr (the one just copied) is not 's' or 'S', increment ptr to point to the next character. This will overwrite any S that was copied.

When the loop exits, copy the source character to ptr one last time. This loads the ending '\0'. Your string should now be copied, and ptr should now contain no S's.

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