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100pt question malloc()

Posted on 2000-04-30
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Last Modified: 2010-04-02
Here is the question for 100 pts! help :)
 
http://www.experts-exchange.com/jsp/qShow.jsp?ta=cprog&qid=10336579 
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Question by:cisk
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pitonyak earned 50 total points
ID: 2764929

I looked at your code and you are freeing the code malloced code, but
I suspect that this is not what you intended to do.
The problem is that all that you are doing is simply freeing memory.
For example, your code there are the following three lines:

   printf("Before free %s --- ", tbp->entry[j].name);
   free(tbp->entry[j].name);
   printf("After free %s\n", tbp->entry[j].name);

The first line is OK assuming that you do not have a null pointer.
The second line is ok because the memory was malloced.
The third line is WRONG because you printed memory that you just deleted.
What you really want to do is to swap the names.
I assume that nothing else points to the memory so you could do this as follows:


for(i=0; i < n; i++) {
   for(j=0; j< n-1; j++) {
      if(strcmp(tbp->entry[j].name, tbp->entry[j+1].name) > 0) {
         // switch names
         char* temp = tbp->entry[j].name;
         tbp->entry[j].name = tbp->entry[j+1].name;
         tbp->entry[j+1].name = temp;
         // switch the phone numbers
         temp = tbp->entry[j].telNum;
         tbp->entry[j].name = tbp->entry[j+1].telNum;
         tbp->entry[j+1].telNum = temp;
      }
   }
}

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Expert Comment

by:843988
ID: 2928069
I agree your answer, pitonyak
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Author Comment

by:cisk
ID: 2929257
Adjusted points from 0 to 50
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by:cisk
ID: 2929260
Comment accepted as answer
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LVL 1

Author Comment

by:cisk
ID: 2929261
I'm sorry but i canceled this question a long time ago and i guess i thought it was going to delete this one too.. i figured out why a few minutes after i pointed..

 BUT i'm going to ago ahead and ive 50 points to pitonyak because he was right and he answered in 2 hours
=)
cool?
Cisk
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