hello all, i am having a real hard time tracing down a logic problem and am looking for help. this program just does a binary search on a sorted list and returns a record. now it works for records that exist. however, i want it to continue searching until an exit code is given. that works as well. the problem is coming when i search for a record that does not exist. it will print and error, but then when i search for an existing record it tells me it does not exist.
any clues? below is the c code the data is a byte file so i cant upload it.
code:
/**************************************************************************************************
Devang N. Joshi *
Homework Four *
CSCI 325 - Binary Search *
March 7th, 2011 *
*
The purpose of this program is to implement a binary search on sorted data *
**************************************************************************************************/
#include <ctype.h> //
#include <stdio.h> //<--header files //
#include <stdlib.h>
#include <stdbool.h> //
/*************************************************************************************************/
struct Faculty_Info //
{ //
char fname[15],lname[15]; //
int phone, office; //<--data structure for faculty info //
char dept[5]; //
}; //
/*************************************************************************************************/
void main () //
{ //
//
struct Faculty_Info TEMP; //<--declare a TEMP data structure //
FILE *Infile; //<--declare file handler //
int status, min, max, mid; //<--declare interger values for binary search //
float test; //<--declare float test for binary search division //
long location; //<--declare type "long" for the location of data //
char searchName[20]; //<--declare char for user input of search //
bool loopStop = false;
//
//
//
//
/*Open sorted datafile, check for errors*/ //
Infile = fopen ("faculty_sorted.dat","r"); //
if (Infile == NULL) //
{ //
fprintf(stderr, "\nError opening input file!\n\n"); //
exit (1); //
} //
//
/*set min equal to one, needed for search to work*/ //
min=1; //
fread (&max, sizeof(int), 1, Infile); //<--read file //
fprintf(stderr, "\nEnter last name to search (or type 'exit'): "); //<--user input //
scanf( "%s", searchName ); //of name to search //
//
while (strcmp(searchName,"exit")!=0) //
{ //
//
searchName[0]=toupper(searchName[0]); //
//
mid = (min + (max - min)) / 2; //<--get midpoint //
mid--; //fix midpoint back one, to read the record //
//
/*set location by midpoint*/ //
location = sizeof(int) + sizeof(struct Faculty_Info)*mid; //
/*from location search record */ //
fseek (Infile, location, SEEK_SET); //
/*for the wanted record*/ //
fread (&TEMP, sizeof(struct Faculty_Info), 1, Infile); //
test=max/2; //
//
/*while the record is not found, divide search*/ //
while(strcmp(TEMP.lname,searchName)!=0) //
{ //
test=test/2; //<--size by two (binary search, keep splitting) //
//
if (test<=0) //
{ //
//
/*if test < 0, you do not have the record, //
you have fallen out of the list bounds, //
print error //
*/ //
fprintf(stderr, "\nRecord not found-1\n\n");
goto END;
} //
//
if(strcmp(searchName,TEMP.lname)==0) //
{ //
min = mid + 1; //<--you have found the record, bring up the min //
} //
else //
{ //
max = mid - 1; //<--you have not found the record, keep searching//
} //
//
mid = (min + (max - min)) / 2; //<--recalculate midpoint //
mid--; //<--push min back //
//
location = sizeof(int) + sizeof(struct Faculty_Info)*mid; //
/*continue to search the list*/ //
fseek (Infile, location, SEEK_SET); //
fread (&TEMP, sizeof(struct Faculty_Info), 1, Infile); //
//
}//while //
//
/* //
if max > or = min, you have searched all records, //
its not in the list, print error //
*/ //
if(max>=min) //
{ //
fprintf(stderr, "\nRecord not found-2\n\n"); //
goto END;
}
printf("\nFirst Name: %s\n", TEMP.fname);
printf("Last Name: %s\n", TEMP.lname);
printf("Extension: %d\n", TEMP.phone);
printf("Office Number: %d\n", TEMP.office);
printf("Department: %s\n\n", TEMP.dept);
//loopStop = false;
END: //
/*set min equal to one, needed for search to work*/ //
min=1; //
fread (&max, sizeof(int), 1, Infile); //<--read file //
//
/*user input another name or exit code*/ //
fprintf(stderr, "\nEnter last name to search (or type 'exit'): "); //
scanf( "%s", searchName );
//
}//while //
//
fclose(Infile); //<--close the datafile //
//
} //
/*************************************************************************************************/
