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Qsort problems...

Posted on 1999-01-13
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Last Modified: 2010-04-15
having problems with qsort. I use watcom c/c++

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


int compare( const void *op1, const void *op2 )
  {
    const char **p1 = (const char **) op1;
    const char **p2 = (const char **) op2;
    return( strcmp( *p1, *p2 ) );
  }

void main()
  {
    char CharVect[3][10] = {{'\0'}};

    strcpy(CharVect[0],"last");
    strcpy(CharVect[1],"middle");
    strcpy(CharVect[2],"first");

    qsort( CharVect, 3,
          sizeof(char), compare );
    printf( "%s %s %s\n",
            CharVect[0], CharVect[1], CharVect[2] );
  }

does not sort...any suggestions ?
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Question by:migue
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5 Comments
 
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Expert Comment

by:imladris
ID: 1255847
You don't need the compare function and the width is wrong. You should be able to do:

qsort(CharVect,3,10,strcmp);

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LVL 16

Expert Comment

by:imladris
ID: 1255848
Note: the 10 is sizeof(CharVect[0]). Also qsort is expecting the elements to be presented in a block of memory (as CharVect is) and so simply passes pointers to the compare function, not pointers to pointers (it "knows" where the elements are given the information about the base address and the width).

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LVL 14

Expert Comment

by:AlexVirochovsky
ID: 1255849
1. wrong answer!
2. >>    qsort( CharVect, 3,   sizeof(char), compare ); <--error!
  must be:  qsort( CharVect, 3,   sizeof(char *), compare );

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Author Comment

by:migue
ID: 1255850
answer is simply incorrect. I would like to cancel this issue, I wrote a quick sort myself.
Alex might be right.
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Accepted Solution

by:
AlexVirochovsky earned 100 total points
ID: 1255851
My answer: my previous comment.
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