I am having trouble with a binary search on strings in c. I use the strcmp function to compare the strings, but I still get no output when I type in a name that I know is in the list.
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#define MAX_STRING_LEN 25
void insert_sata(char **strings, const char* filename, int size);
void allocate( char ***strings, int size);
int binary_search(char **strings, char *target, int start_idx, int end_idx);
int main(int argc, char* argv[]){
if(argc != 4){
printf("Wrong number of args");
}
char **pointer;
int size = atoi(argv[1]);
allocate(&pointer, size);
insert_data(pointer, argv[2], size);
int x;
int z = 1;
char search_name[MAX_STRING_LEN];
while( z == 1){
printf("\nEnter a name to search for: ");
scanf("%s", search_name);
x = binary_search(pointer, search_name, 0, size);
printf("\nContinue searching names? ( 1 = yes, 0 = No):");
scanf("%d", &z);
}
}
void allocate(char ***strings, int size){
int i;
*strings = malloc(sizeof(**strings) * size);
for( i = 0; i < size; i++)
{
(*strings)[i] = malloc(sizeof(char) * MAX_STRING_LEN);
}
}
void insert_data(char **strings, const char* filename, int size){
FILE *input;
input = fopen(filename, "r");
int i;
for (i = 0; i < size; i++){
fscanf(input,"%24s", strings[i]);
}
fclose(input);
}
int binary_search(char **strings, char *target, int start_idx, int end_idx){
int result;
int mid_idx = 0;
while( end_idx >= start_idx){
mid_idx = (end_idx + start_idx) / 2;
result = strcmp(strings[mid_idx], target);
if(result > 0){
end_idx = start_idx - 1;
}
else if (result < 0){
start_idx = mid_idx + 1;
}
else if( result == 0){
printf("%s was found in the set", target);
}
}
}
The binary search is the function that is giving me trouble. I do not recieve any seg faults or anything, just nothing is displayed when I search a name that is in the file. Here is the list of names that I scan into the program.
- matt
- susan
- mark
- david
- aden
- phil
- erik
- john
- caden
- mycah
