CODEWITHSUNDEEP
carrays
user1509423
user1509423

Reputation: 1

Array debugging C?

An assignment in the K&R C Programming 2nd edition says that I have to write a program to print a histogram of the lengths of words in its input. I believe I know how to do so, but when running a test program on arrays, which I have only just learned about, all I get is "8", no matter what I input. This is the program so far:

#include <stdio.h>

/* write a program to print a histogram
of the lengths of words in its input */
main()
{
      int wl[11];
      int cc, c;

      while ((c=getchar()) != EOF);
      {
            if (c != ' ')
               ++cc;
            if (c == ' ' && cc == '1')
            {
               ++wl[0];
               c = 0;
            }
       putchar(wl[0]);
      }
}

It may be just because I'm a total beginner in programming, but I honestly cannot see where I went wrong here. Any help would be appreciated.

Upvotes: 0

Views: 179

Answers (3)

Josh Petitt
Josh Petitt

Reputation: 9589

I'd use argc and argv here (look this up in your C book). The nice thing about this is it gives you the number of words and you don't have to handle input yourself (let the OS and your standard library handle it). You could malloc the sizes array (the histogram buckets), but you could also make a "reasonable" assumption that will get the majority of English words (hopefully you aren't German :-) ).

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

// assume longest word is "Supercalifragilisticexpialidocious"    
#define MAX_WORD_LENGTH    (35)

int main(int argc, char* argv[])
{
  size_t sizes[MAX_WORD_LENGTH] = {0};

  for (int i=0; i<argc; ++i)
  {
    size_t len = strlen(argv[i]);

    if (len < MAX_WORD_LENGTH)
    {
      ++sizes[len]; // increment bucket
    }
    else
    {
      ++sizes[0]; // too long, put in default bucket
    }
  }

  // print the buckets
  for (int i=1; i<MAX_WORD_LENGTH; ++i)
  {
    printf("%d ", sizes[i]); 
  }

  // print the default bucket
  printf("%d", sizes[0]);
}

Upvotes: 0

Jerry Coffin
Jerry Coffin

Reputation: 490408

You have a number of problems here.

main()

Though it was fairly common to omit the return type at that time, it isn't any more. You probably want to write this as:

int main()

Instead.

{
      int wl[11];

As @D.Shawley already pointed out, this will contain garbage.

      int cc, c;

What he forgot to point out was that these will too. This doesn't matter much for c, but does for cc.

      while ((c=getchar()) != EOF);
      {
            if (c != ' ')
               ++cc;

Here you're incrementing cc, but you never set it to a known value first, so you have no idea what it started as, or (therefore) what result your increment will produce.

            if (c == ' ' && cc == '1')

I'm guessing you don't really want '1' here -- you probably just want 1. That is, you don't want to compare cc to the digit '1', but to the value 1.

            {
               ++wl[0];
               c = 0;

Though it's harmless, zeroing c doesn't accomplish much here -- maybe you wanted to zero cc? I'm not sure what you're really trying to do though. At a guess, you probably don't want to increment wl[0] either.

            }
       putchar(wl[0]);

You probably don't want putchar here either -- you probably want to write out wl[0] as an int or (to produce a histogram) use it as the count of something like '*' to print out.

Upvotes: 1

D.Shawley
D.Shawley

Reputation: 59583

Start by initializing your variables:

int wl[11] = {0};
int cc = 0;

By default, memory contains garbage in C.

EDIT: Beyond the Obvious

  • the comparison cc == '1' does not do what you expect. It should probably be cc == 1
  • my guess is that ++wl[0] should be ++wl[cc]. This assumes a maximum word length of 11.
  • c = 0 should be resetting cc instead - c is the current character, cc is the current word length
  • putchar needs a character not an int so you will need to solve that as well

Good start though.

Upvotes: 2

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