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sorting a structured array

Posted on 1999-01-13
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Last Modified: 2010-04-15
hope somebody could really help me quick.  here's the problem:
note: i'm using UNIX OpenPlatform V with C language....
below is a sample structure -
typedef struct
{
    int emplno;
    char emplname[25+1];
    char date[10+1];
    long reghrs;
    long vachrs;
    long sickhrs;
} EMPLOYEE;

main()
{
    EMPLOYEE emp;
note: the number of employees is unknown.
/******************************************/
now the problem, how would i sort this database by date, by emplno and then by reghrs?  this report should be able to run at anytime and number of records in the database is unknown.  do i always need to calculate how many records the database has?

please, if anybody has ideas... i really need help as fast as i can.  i'm running out of people to ask.  thanks a bunch.
zandy1.
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Question by:zandy1
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Expert Comment

by:rbr
Comment Utility
What  do you mean the number is unknow. If it`s unknow by compile-time nor probelm

int my_comp (void *p1, void *p2)
{
  EMPLOYEE *pe1=p1;
  EMPLOYEE *pe2=p2;
  int comp;

  if ((comp=strncmp (pe1->date,pe2->date,11)) != 0)
     return (comp);
  if (pe1->emplno != pe2->emplno)
     return (pe1->emplno - pe2->emplno)
  if (pe1->reghrs >pe1->reghrs)
     return (1);
 if (pe1->reghrs <pe1->reghrs)
     return (1);
return (0);
}


EMPLOYEE *pemp;

anz=100; /* could be any number */
pemp = (EMPLOYEE *)calloc(anz;sizeof(EMPLOYEE));

get the data (by reading in from a file or somethink else */
qsort (pemp,anz,sizeof(EMPLOYEE),my_comp);

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Author Comment

by:zandy1
Comment Utility
thank you for the reply but i still don't get it.  from the hint you replied to me, i did the following function changing the sort a bit. THE STRUCTURE IS STILL THE SAME! i would like it to sort now by emplno then be date and nothing works. it keeps printing the last record after it sorts the file. if anybody could give me an answer and put me in a correct way, i'd really appreciate it. PLEASE help anybody.... below is the function:
/*----------------------*/
PRWK prwk;

int rdprwk(char *whsin, PRWK *prwkrec)
{
   PRWK *tmpprwk;
   int cnt = 100;

   fp = fopen(filename,"r+");  /*open file*/
   if(fread(&prwk,sizeof(PRWK),1,fp)
   do { printf(".....etc");           /*read database unsorted*/
        fread(&prwk,sizeof(PRWK,1,fp);
      }while(!feof(fp));

   tmpprwk=(PRWK *)calloc(cnt,sizeof(PRWK));  /*per example*/
   qsort(tmpprwk,cnt,sizeof(PRWK),my_comp);  /*per example*/
   for(ctr=0,ctr<cnt;ctr++)
   {printf("....etc"); }    /*problem: only prints last record*/
   
   /*------MY_COMP FUNCTION----*/
int my_comp(const void *p1,const void *p2)
{
    PRWK *pe1=p1;
    PRWK *pe2=p2;
    int comp;

    if(pe1->emplno != pe2->emplno)
       return(pe1->emplno - pe2->emplno);
    if((strcmp(pe1->date,pe2->date,11)!=0))
       return(comp);
}
/*---------------------END OF FUNCTIONS---*/
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Expert Comment

by:rbr
Comment Utility
Ok I see your problem. Try this
/*----------------------*/
 
int rdprwk(char *whsin, PRWK *prwkrec)
{
PRWK *tmpprwk;
int cnt = 0,i=0;

fp = fopen(filename,"r+");  /*open file*/
if(fread(&prwk,sizeof(PRWK),1,fp)
do { printf(".....etc");           /*read database unsorted for getting the number*/
               fread(&prwk,sizeof(PRWK,1,fp);
      cnt++;
}while(!feof(fp));
fclose (fp);

tmpprwk=(PRWK *)calloc(cnt,sizeof(PRWK));  /*per example*/
fp = fopen(filename,"r+");  /*open file*/
if(fread(&prwk,sizeof(PRWK),1,fp)
do { printf(".....etc");           /*read database unsorted*/
               fread(&(tmpprwk[i]),sizeof(PRWK,1,fp);
i++;
}while(!feof(fp));
fclose (fp);
qsort(tmpprwk,cnt,sizeof(PRWK),my_comp);  /*per example*/
for(ctr=0,ctr<cnt;ctr++)
          {printf("....etc"); }    /*problem: only prints last record*/
           
          /*------MY_COMP FUNCTION----*/
       int my_comp(const void *p1,const void *p2)
       {
           PRWK *pe1=p1;
           PRWK *pe2=p2;
           int comp;

           if(pe1->emplno != pe2->emplno)
              return(pe1->emplno - pe2->emplno);
           if((strcmp(pe1->date,pe2->date,11)!=0))
              return(comp);
       }
       /*---------------------END OF FUNCTIONS---*/
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Author Comment

by:zandy1
Comment Utility
hi rbr,
again - thank you very much for the quick response and the sample you gave me - unfortunately, it didn't work.  i followed your sample to the letter and i still get the same output.  only the last record read is being printed 4 times (value of cnt).  would you or any of you friends have anymore ideas?  thanks for the time - please don't give up on me.
zandy1
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Expert Comment

by:ozo
Comment Utility
Where are you printing the record?
Also, where are you setting comp?
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Accepted Solution

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rbr earned 130 total points
Comment Utility
How do you print ?
Try
for(ctr=0,ctr<cnt;ctr++)       printf("%d,%s,%s,%ld,%ld,%ld\n",tmpprwk[ctr].emplno,tmpprwk[ctr].emplname,tmpprwk[ctr].date,tmpprwk[ctr].reghrs,tmpprwk[ctr].vachrs,tmpprwk[ctr].sickhrs);
       
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Expert Comment

by:rbr
Comment Utility
Change pls
 int my_comp(const void *p1,const void *p2)
              {
                  PRWK *pe1=p1;
                  PRWK *pe2=p2;

                  if(pe1->emplno != pe2->emplno)
                     return(pe1->emplno - pe2->emplno);
                  return(strcmp(pe1->date,pe2->date,11));
                     return(comp);
              }
         
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by:rbr
Comment Utility
Sorry mistake with copy and paste use
int my_comp(const void *p1,const void *p2)
                     {
                         PRWK *pe1=p1;
                         PRWK *pe2=p2;

                         if(pe1->emplno != pe2->emplno)
                            return(pe1->emplno - pe2->emplno);
                         return(strcmp(pe1->date,pe2->date,11));
                           
                     }
           
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Expert Comment

by:rbr
Comment Utility
And use strncmp instead of strcmp if you pass a length. if your strings are \0 terminated you can use strcmp without 11.
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by:zandy1
Comment Utility
thanks rbr!!
thank you very much for your quick response.
zandy1
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