I'm trying to implement a hash table in C. I have a csv file, which only consists of a list of surnames on separate lines each. e.g.
Synott
O Neill
Potter
that I am to read from. I then use a hash function, called hash1, to convert these strings into an integer which would give me my index for my hash table. I am then to store the frequency of the occurrence of each name. However, I am getting a segmentation fault which I have deduced is coming from my
void insert(struct individual *p)
function. I'm clueless as to how to solve this and have only started practising C.
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#define maxSize 500
/* Hash function that returns my key as an integer, giving me my index */
int hash1(char *s){
int hash = 0;
while(*s){
hash = hash + *s;
s++;
}
return hash;
}
/* Item to be stored */
struct individual{
int frequency; /* Value to be stored */
char name[50]; /* This is will be my key */
};
/* The hash table */
struct individual *hashArray[maxSize];
/* Initialising hash table */
void initArray(){
for (int i = 0; i < maxSize; i++){
hashArray[i]->frequency = 0;
hashArray[i]->name[i] = 0;
}
}
/* Function to load the names */
int next_field(FILE *f, char *buffer, int max){
int i = 0, end = 0;
for(;;){
buffer[i] = fgetc(f);
if(buffer[i] == '\n' || feof(f)){ end = 1; break; }
}
buffer[i] = 0;
return end;
};
/* Loading the names into structs - Done */
void reader(FILE *f, struct individual *n){
char buf[50];
next_field(f, n->name, maxSize);
};
/* Adding to the hash table */
void insert(struct individual *p){
struct individual *person = malloc(sizeof(struct individual));
int index = hash1(p->name) % maxSize;
// The issue is coming from this line here:
int primaryIndex = hash1(hashArray[index]->name) % maxSize;
/* Linear Probing */
printf("Do I get to here\n");
while(hashArray[index] != NULL){
if(primaryIndex == index){
hashArray[primaryIndex]->frequency++;
} else{
++index; /* Going to next block */
}
index %= maxSize; /* Looping through the hash table */
}
hashArray[index] = person;
};
void display(struct individual *duine){
printf("%s\n", duine->name);
};
int main(int argc, char *argv[]){
FILE *list;
struct individual in;
//initArray();
/* Opening file */
if( argc < 2 ) {
printf("Also include csv file name.\n");
return EXIT_FAILURE;
}
/* Checking if file is found */
list = fopen(argv[1], "r");
if(!list) {
printf("File not found. %s\n", argv[1]);
return EXIT_FAILURE;
}
while(!feof(list)){
reader(list, &in);
insert(&in);
display(&in);
}
fclose(list);
return EXIT_SUCCESS;
}
What I'm trying to do here is to compare two indices, one from the struct p being passed into this function and one from the hash table at this index. If they are the same, I wish to increase the frequency count stored there by 1. If I do remove this line, the rest of my code runs fine.
Thank you very much
