help in using binary search

[huskers]

Hi,

Trying to do a binary search but couldnt figure out where I am going wrong any help is greatly appreciated. I have product id and quantity as columns in database table and I am loading from the table to an array of structures. I am trying to find the quantity for a particular structure using binary search but it doesnt return the correct value.

#define MAX 3000

typedef struct {
long prodid;
long quantity;
} myrecords;

myrecords memdb[MAX];

main()
{
long prod_id, quant;
myrecords *p;

prod_id = 1874;

loadDBmem();
p = bsearch(&prod_id, memdb, MAX, sizeof(myrecords), comp);

printf("quantity: %d, product ID: %d\n", p->quantity,
p->prodid);

}

int comp(const void *a, const void *b)
{
long *myarray;
myarray = (long *)b;

if( *(long *)a == *myarray)
{
return 0;
}
else if( *(long *)a > *myarray)
{
return 1;
}
else
{
return -1;
}

}

int loadDBmem()
{
connect to database;
load product id and quantity into array of structures;
disconnect from database;
}

Thanks

 

[victorv]

hi,

I belive your comp function would play as:

int comp(const void *a, const void *b)
{
struct myrecords *p1, *p2;

p1 = (*myrecords) a ;
p2 = (*myrecords) b ;

return( p1->quantity - p2->quantity )

}

P.S.: it seems to me that memdb has to be sorted before.
(use qsort)


bye