Programming

Hi, im trying to create a C program that will count the number of characters, duplicate characters and non duplicate characters in a file and output this to the screen. Here is my code so far:

Code:

#include <stdio.h>

int main( void )

{
char c;
int duplicate = 0;
int nonduplicate = 0;
int count = 0;
char lastChar;

while ( (c = getchar()) != EOF)
       count ++;
       lastChar += c;
{
  if(c = lastChar)
    duplicate ++;
  else( duplicate == duplicate);
}

nonduplicate = (count - duplicate);
printf( "%d %d %d \n", count, duplicate, nonduplicate );

}

This outputs the answer: 67 1 66

It is counting the total characters correctly, but the number i have for my particular test file is 6 duplicates, so i need the answer to display 67 6 61, my main problem is i cant seem to be able to store the last read character so it can find out if the next char is the same. Im probably leaving/forgetting something simple here.
Any help would be appreciated.

Is this a duplicate letter "A"
ABCDEA

Or is this your meaning of duplicate?
AABCDE

I think the last...
To compare the input with the previous character the loop should be something like:

Code:

while ((c = getchar()) != EOF) {
  count++;
  if(c == lastChar){
    duplicate++;
  }
  else {
    lastChar = c;
  }
}

Lots of problems in that code.

This is one:

Code:

while ( (c = getchar()) != EOF)
       count ++;
       lastChar += c;
{
  if(c = lastChar)
    duplicate ++;
  else( duplicate == duplicate);
}

What that really does is this:

Code:

while ( (c = getchar()) != EOF)
{
       count ++;
}

       lastChar += c;
{
  if(c = lastChar)
    duplicate ++;
  else( duplicate == duplicate);
}

That's a big difference.

Note also that getchar() returns an int, not a char. So you can't read the valid character input that corresponds to the truncated integer value of EOF, whatever that value happens to be on your system.

Also, you're not properly initializing your lastChar variable, so you never know what you're comparing it too when you start. Because you could read any character from the stream, your lastChar variable should probably be an int instead of a char, and you could initialize it to something like EOF to make sure it starts with a value that isn't a valid char value.

Not only that, you're doing an assignment instead of a comparison in your if statement. This:

Code:

  if(c = lastChar)
    duplicate ++;

should be:

Code:

  if(c == lastChar)
    duplicate ++;

I'd do something like this:

Code:

int main( void )
{
    int c;
    int last = EOF;
    int dupes = 0;
    int count = 0;

    while ( 1 )
    {
        c = getchar();
        if ( EOF == c )
        {
            break;
        }

        count++;

        if ( last == c )
        {
            dupes++;
        }

        last = c;
    }

    printf( "%d %d %d\n", count, dupes, count - dupes );

    return( 0 );
}

You will note that I deliberately avoided placing ANY assignment statement inside a conditional clause. Most compilers in my experience provide for a warning when they encounter an assignment in a conditional clause. If you make a point of never putting assignment statements in a conditional clause, you can then use that warning capability to find and fix mistakes in your code.

Because you will make mistakes when you code. Anyone who says they write mistake-free and bug-free code is lying or deluded, plain and simple.

Note also that I always used { and } after my conditional clauses. Always using braces even for one-line conditional code makes mistakes like the one you made with your while-loop impossible to make.

Don't pay attention to how code is laid out in textbooks. In textbooks, whitespace and extra lines cost the publisher money.