Need help with С language

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Hi I have two programs, I need to make one of them

I am typing from the keyboard to the console. need to swap the first and last letter of each word and count how many words in total

I hope you will help me)

What I have tried:

first program. Counts the number of words in a sentence:

#include <stdio.h>
#include <string.h>
#define DELIM " \t\n"
 
size_t wc(char * str, const char * delim) {
    return ( strtok(str, delim) ) ? 1 + wc(NULL, delim) : 0;
}
 
 
int main(void) {
    char buf[BUFSIZ];
    
    while ( printf("String: ") && fgets(buf, BUFSIZ, stdin) && *buf != '\n' )
        printf("%lu word(s).\n", wc(buf, DELIM));

    return 0;
}

second program. swaps the first and last letter of each word:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
char * swap(const char * str);
 
int main(void)
{
    const char * str = "geeks for geeks t";
    char * swapped = swap(str);
 
    puts(str);
    puts(swapped);
 
    free(swapped);
    return 0;
}
 
char * swap(const char * str)
{
    const size_t length = strlen(str);
    char * ch = malloc(length + 1);
 
    strncat(ch, str, length);
    ch[length] = '\0';
 
    char * k = ch;
 
    while (k != NULL)
    {
        char * last = strchr(k, ' ');
 
        if (last != NULL)
        {
            char t = *k;
            *k = *(last - 1);
            *(last - 1) = t;
            k = last + 1;
        }
        else
        {
            char t = *(k);
            *k = *(ch + length - 1);
            *(ch + length - 1) = t;
            k = NULL;
        }
    }
 
    return ch;
}

Posted 8-Dec-21 8:35am

Member 15460459

Updated 8-Dec-21 20:00pm

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Rick York 8-Dec-21 16:10pm

OK, help you with what? You have not actually asked a question.

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OriginalGriff · Answer 1 · 2021-12-08T09:10:00

Compiling does not mean your code is right! :laugh:
Think of the development process as writing an email: compiling successfully means that you wrote the email in the right language - English, rather than German for example - not that the email contained the message you wanted to send.

So now you enter the second stage of development (in reality it's the fourth or fifth, but you'll come to the earlier stages later): Testing and Debugging.

Start by looking at what it does do, and how that differs from what you wanted. This is important, because it give you information as to why it's doing it. For example, if a program is intended to let the user enter a number and it doubles it and prints the answer, then if the input / output was like this:

Input   Expected output    Actual output
  1            2                 1
  2            4                 4
  3            6                 9
  4            8                16

Then it's fairly obvious that the problem is with the bit which doubles it - it's not adding itself to itself, or multiplying it by 2, it's multiplying it by itself and returning the square of the input.
So with that, you can look at the code and it's obvious that it's somewhere here:

C

int Double(int value)
   {
   return value * value;
   }

Once you have an idea what might be going wrong, start using the debugger to find out why. Put a breakpoint on the first line of the method, and run your app. When it reaches the breakpoint, the debugger will stop, and hand control over to you. You can now run your code line-by-line (called "single stepping") and look at (or even change) variable contents as necessary.
Think about what each line in the code should do before you execute it, and compare that to what it actually did when you use the "Step over" button to execute each line in turn. Did it do what you expect? If so, move on to the next line.
If not, why not? How does it differ?
Hopefully, that should help you locate which part of that code has a problem, and what the problem is.
This is a skill, and it's one which is well worth developing as it helps you in the real world as well as in development. And like all skills, it only improves by use!

KarstenK · Answer 2 · 2021-12-08T20:00:00

You need to understand the C strings at first: they are char arrays. And your str is some fixed memory string, so dont work with it, but allocate some copy.

And reversing means: take the last char into the first result char buffer and than loop backwards, so some

C++

for( int i = len - 1; i > 0; i-- )

Best is to read some C string tutorial to dive into the basics.

Need help with С language

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