help with mergersort im kind of confused

[rockerjhr]

I need to use mergesort to sort the data in a file that has the names and ages of 10 different people , first i have to sort the names in ascending ascii order and then i have to sort them by their age but im not sure how to do it this is what i have so far

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#define NUMBER_OFPEOPLE 10

typedef struct{

char name[6] ;
int age ;

}people ; 



typedef char byte ; 

void memcopy( byte *to, byte *from, int count ) {  
  
  while (count-- > 0 ) 
    *to++ = *from++ ;

}

int compare_age(  byte *a , byte *b ) {
  
int aa ;
int bb ; 

 aa = ((people *)a)->age ;
 bb = ((people *)b)->age ;

 if (aa < bb) return 1 ;
 if (aa > bb) return -1 ;
   
return 0 ;
}

int compare_name(  byte *a , byte *b ) {

char aa[6] ;
char bb[6] ;

 strcpy(aa, ((people *)a)->name) ;
 strcpy(bb, ((people *)b)->name) ;

 return strcmp(aa, bb) ;

}

void merge_sort(byte data[], int n , int elementsize , int (*p_cmp_f)() ) ;



int main(void){

  int j, n = 10 , i;

people *A ;



people s ;



A=(people *)malloc(sizeof(people)*n) ; 

 if ( A == NULL ) { printf(" Error mallocing \n" ); return -1 ; } 


FILE *fp ;
fp = fopen("people","r") ;
for(j = 0 ; j < 10 ; j++){
fscanf(fp, "%s %d\n",&s.name,&s.age); 

}


  merge_sort( (byte *) A, n , sizeof(people) , compare_name ) ;

  for(j = 0 ; j < 10 ; j++ ) printf("%s"  "%d" , s.name,s.age) ;

  merge_sort( (byte *) A, n , sizeof(people) , compare_age ) ;

  for(i = 0 ; i < 10 ; i++ ) printf("%d"  "%s" , s.age,s.name) ;

return 0 ;

}


















void merge_sort( byte data[], int n, int elementsize, int (*p_cmp_f)( ) )  {

byte *firsthalf ; 
byte *endoffirsthalf ; 
byte *secondhalf ; 
byte *endofsecondhalf ;
byte *resultbuffer , *p_result ; 
int halfsize ; 

if(n <= 1) 
return ; 

halfsize = n/2 ; 
firsthalf = data ; 
secondhalf = data + halfsize * elementsize ; 

merge_sort(firsthalf ,halfsize,elementsize, p_cmp_f) ;
merge_sort(secondhalf,n-halfsize,elementsize,p_cmp_f) ; 

endoffirsthalf = secondhalf ; 
endofsecondhalf = data + n * elementsize ; 
resultbuffer = (byte *) malloc(n * elementsize); 
 p_result = resultbuffer ; 

while(firsthalf < endoffirsthalf && secondhalf < endofsecondhalf ){

if((*p_cmp_f)(firsthalf,secondhalf) < 0) {
memcopy(p_result , firsthalf , elementsize) ; 
firsthalf += elementsize ; 
} else{
memcopy(p_result , secondhalf , elementsize);
secondhalf += elementsize ; 
}

p_result += elementsize ;
 
}
while(firsthalf < endoffirsthalf){
memcopy(p_result,firsthalf,elementsize) ; 
firsthalf += elementsize ; 
p_result += elementsize ; 

}

while( secondhalf < endofsecondhalf){
memcopy(p_result , secondhalf , elementsize ) ; 
secondhalf += elementsize ; 
p_result += elementsize ; 

}
memcopy(data,resultbuffer, n * elementsize) ; 
free(resultbuffer) ;


}

[WolfPack]

Please tell us what part you are having problems with. Data reading from the file part? Sorting the names in ascending order? or Sorting the ages?
If you are getting compile or link errors, post them.
If you are getting incorrect output, post the input and the output(both expected output and actual output).
It is boring to look through 160+ lines of code without having no idea what we are looking for..

[rockerjhr]

It compiled I am having problems with the sorting part it doesnt sort anything it just prints out the the name at the bottom of the list 10 times when i run it

input would be something like this

noble 12
nolan 27
nicky 34
scott 38
simon 45
tylor 29
zenas 6
wells 55
vince 19
toney 24

and output would just print : toney 24 10 times

i think my compare_name and compare_age functions are not correct

[Adak]

When you run across the merry prankster who convinced you to use that sorting code, kick 'em in the a**.

I've looked through this a few times, and it's a toss up between cussing and laughing, I can tell you. ;)

By all means, narrow down the problem! The worst thing in programming, is to have 100 lines of code, in several functions, and then find out "oops!", and have NO IDEA where the error is.

Check major blocks of code, and all functions, as you're programming:

1) Are they syntactically correct (compile w/o errors)?
2) Are they accurate across the range of data you'll be dealing with?

You'd be amazed at how often stupid errors are not found early on, easily, simply because the programmer was "in a hurry". Later, it takes 5 X as long to find the error.

[rockerjhr]

@Adak if you werent going to help why bother replying? this forum sucks no help at all

but anyways i fixed the mistakes i made i was just reading the data incorrectly and then i didnt do anything with the space i malloced up just copied the data to S and printed it instead of putting it in A and had to fix my compare function

heres my code

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#define NUMBER_OFPEOPLE 10

typedef struct {

  char name[6] ;
  int age ;

} people ; 

typedef char byte ; 

void memcopy( byte *to, byte *from, int count ) {  
  
  while (count-- > 0 )  *to++ = *from++ ;

}

int compare_age(  byte *a , byte *b ) {
  
  int aa ;
  int bb ; 

   aa = ((people *)a) -> age ;
   bb = ((people *)b) -> age ;

  if (aa > bb) return 1 ;

  if (aa < bb) return -1 ;
   
  return 0 ;
}

int compare_name(  byte *a , byte *b ) {

  char aa[6] ;
  char bb[6] ;

 strcpy(aa, ((people *)a) -> name) ;
 strcpy(bb, ((people *)b) -> name) ;

 return strcmp(aa, bb) ;

}

void merge_sort(byte data[], int n , int elementsize , int (*p_cmp_f)() ) ;

int main( int argc, char *argv[] ) {

  int j, n = 10  ;

  FILE *fp ;

  people *A ;

  people s ;

  A = (people *)malloc(sizeof(people) * n ) ; 

 if ( A == NULL ) { printf(" Error mallocing \n" ); return -1 ; } 

  fp = fopen("people","r") ;

  for ( j = 0 ; j < 10 ; j++ ) {

    fscanf(fp, "%s %d\n", &s.name[0], &s.age ) ; 

    A[j] = s ;

  }

  merge_sort( (byte *) A, n , sizeof(people) , compare_name ) ;

  for(j = 0 ; j < 10 ; j++ ) printf("%s   %d\n" , A[j].name, A[j].age) ;

  merge_sort( (byte *) A, n , sizeof(people) , compare_age ) ;

  printf("\n") ;

  for( j = 0 ; j < 10 ; j++ ) printf("%d  %s\n" , A[j].age, A[j].name) ;

  return 0 ;

}

void merge_sort( byte data[], int n, int elementsize, int (*p_cmp_f)( ) )  {

byte *firsthalf ; 
byte *endoffirsthalf ; 
byte *secondhalf ; 
byte *endofsecondhalf ;
byte *resultbuffer , *p_result ; 
int halfsize ; 

if(n <= 1) 
return ; 

halfsize = n/2 ; 
firsthalf = data ; 
secondhalf = data + halfsize * elementsize ; 

merge_sort(firsthalf ,halfsize,elementsize, p_cmp_f) ;
merge_sort(secondhalf,n-halfsize,elementsize,p_cmp_f) ; 

endoffirsthalf = secondhalf ; 
endofsecondhalf = data + n * elementsize ; 
resultbuffer = (byte *) malloc(n * elementsize); 
 p_result = resultbuffer ; 

while(firsthalf < endoffirsthalf && secondhalf < endofsecondhalf ){

if((*p_cmp_f)(firsthalf,secondhalf) < 0) {
memcopy(p_result , firsthalf , elementsize) ; 
firsthalf += elementsize ; 
} else{
memcopy(p_result , secondhalf , elementsize);
secondhalf += elementsize ; 
}

p_result += elementsize ;
 
}
while(firsthalf < endoffirsthalf){
memcopy(p_result,firsthalf,elementsize) ; 
firsthalf += elementsize ; 
p_result += elementsize ; 

}

while( secondhalf < endofsecondhalf){
memcopy(p_result , secondhalf , elementsize ) ; 
secondhalf += elementsize ; 
p_result += elementsize ; 

}
memcopy(data,resultbuffer, n * elementsize) ; 
free(resultbuffer) ;


}