Thread: pointer problems

Hello,

I'm pretty new to C programming, and am working on an assignment that uses the quicksort algorithm adapted to sort strings. I got it working OK except for the fact that it only seems to be looking at the first character in each string. I'm at a loss trying to figure out where the problem is. Anyone have any clues?

I'm testing it by piping it the contents of a file named "test" that contains the following:

Code:

bbb
ccc
aaa
ddd

I'm trying to get the output to be:

Code:

aaa
bbb
ccc
ddd

Instead, I'm getting:

Code:

a
b
c
d

Here's how I'm executing it:

Code:

$ cat test | ./a.out

Anyway, here's the c code. Sorry for the huge post.

Code:

//-----------------------------COMPILER DIRECTIVES------------------------------
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <assert.h>

//-----------------------------FUNCTION PROTOTYPES------------------------------
void quicksort( char *[], int );
void swap( char *[], int, int );

//----------------------------------CONSTANTS-----------------------------------
const long LINE_CAP = 1000000;     // Max number of strings (lines)
const short STR_CAP = 82;          // Max characters per string +2 for '/0'

//--------------------------------MAIN FUNCTION---------------------------------
int main() {

// Declare Variables
   long lngLinesRead = 0;          // Keeps track of how many data lines exist
   char *pcLine[LINE_CAP];         // Array of character arrays
   char cLine[STR_CAP];            // Buffer for the array of characters
   int i;                          // Iterator for loops

// Read the char array into the buffer while EOF is not reached
   while( fgets( cLine, STR_CAP, stdin ) != NULL ) {

// Allocate space at the nth pointer in pcLine array
      pcLine[lngLinesRead] = (char *) malloc( sizeof( cLine ) );

// Set the value in the pointer to the value of the character array
      *(pcLine[lngLinesRead]) = *cLine;

// Increment to next line
      lngLinesRead++;
   }

// Sort the lines
   quicksort( pcLine, lngLinesRead );

// Print to standard output
   for( i = 0; i < lngLinesRead; i++ ) {
      printf( "%s\n", pcLine[i] );
      free( pcLine[i] );
   }

// Return error free
   return 0;
}

//-----------------------------FUNCTION DEFINITIONS-----------------------------

// swap:  interchange v[i] and v[j].
void swap( char *v[], int i, int j )
{
	char *temp;

	temp = v[i];
	v[i] = v[j];
	v[j] = temp;
}

// quicksort: sort v[0]..v[n-1] into increasing order.
void quicksort( char *v [], int n )
{
	int i, last;
	if( n <= 1 )                             // nothing to do
		return;

	swap( v, 0, rand() % n );                // move pivot element to v[0]
	last = 0;

	for ( i = 1; i < n; i++ )                // partition
		if ( strcmp( v[i], v[0] ) < 0 )
			swap( v, ++last, i );

	assert(( last >= 0 ) && ( last < n ));
	swap( v, 0, last );                      //restore pivot

	quicksort( v, last );                    // recursively sort each part
	quicksort( v+last+1, n-last-1 );
}

Thanks for the help, I really appreciate it.