pvjc26/du6/a_station.c

#include "a_station.h"
#include <stdlib.h>
#include <string.h>

struct station* create_station(){
   struct station* station = (struct station*)calloc(1,sizeof(struct station));
   station->tracks = (struct car**)calloc(STATION_SIZE, sizeof(struct car*));
   station->track_count = STATION_SIZE;
   return station;
}

void destroy_station(struct station* station)
{
    if (station == NULL)
    {
        return;
    }

    //preiteruje cez kazdy jeden 'track/carar' v poli 'tracks' a
    for (int i = 0; i < station->track_count; i++)
    {
        struct car* currentTracks = station->tracks[i];
        while (currentTracks != NULL)
        {
            struct car* tempTrack = currentTracks;
            currentTracks = currentTracks->next;
            free(tempTrack);
        }
    }
    //uvolnenie pamate vrchnych prvkov/'nodeov'..
    free(station->tracks);
    free(station);
}

int select_track(struct station* station, const char* target)
{
    if (station == NULL)
    {
        return 0;
    }

    // vyuzitie 'djb2' hashovacieho algorithmu..
    unsigned long hash_value = 5381;
    int i = 0;
    
    while (target[i] != '\0') {
        // viacej 'human readable' verzia algorithmu.
        //Pri hashovacich funkciach v programovani je zvykom pouzivat bitwise operator ('>>') na docielenie rovnakeho vysledku
        hash_value = (hash_value * 33) + target[i];
        i++;
    }
    unsigned long index = hash_value % station->track_count;

    return index;
}

void add_target_capacity(struct station* station,const char* target, int capacity)
{
    //helper lok. premeny
    int i = select_track(station, target); //vyber track
    struct car* current = station->tracks[i];
    int lastPosIndex = TARGET_SIZE - 1; //index s poziciou null terminatora

    //iterovnie cez vsetky tracky
    //Pocas iteracie porovna pole s cielovou stanicou pre aktualny smernik/pointer (current->value) versus vstupny argument 'target'
    while (current != NULL)
    {
        if (strcmp(current->value, target) == 0)
        {
            current->capacity += capacity;
            return;
        }
        current = current->next;
    }

    //Poistka -> ak neexistuje novy zaznam, vyvtori ho 
    struct car* newCar = malloc(sizeof(struct car));
    strncpy(newCar->value, target, lastPosIndex);
    newCar->value[lastPosIndex] = '\0'; //null terminovanie..
    newCar->capacity = capacity;

    //vlozi na zaciatok tracku
    newCar->next = station->tracks[i];
    station->tracks[i] = newCar;
}

int get_target_capacity(struct station* station,const char* target)
{
    for (int i = 0; i < station->track_count; i++)
    {
        struct car* currentTracks = station->tracks[i];
        while (currentTracks != NULL)
        {
            if (strcmp(currentTracks->value, target) != 0)
            {
                return currentTracks->capacity;
            }
            currentTracks = currentTracks->next;
        }
    }
    return 0;
}

int count_targets(struct station* station)
{
    if (station == NULL)
    {
        return 0;
    }
    
    int count = 0;
    for (int i = 0; i < station->track_count; i++)
    {
        struct car* currentTracks = station->tracks[i];
        // while (currentTracks->next->value != NULL && currentTracks->next != NULL)
        while (currentTracks != NULL)
        {
            count += 1;
            currentTracks = currentTracks->next;
        }
    }
    return count;
}

int count_capacity(struct station* station){
    int count = 0;
    
    for (int i = 0; i < station->track_count; i++)
    {
        struct car* currentTracks = station->tracks[i];
        while (currentTracks != NULL)
        {
            //skontroluje individualne ich int 'capacity' pole a inkrementuje do vysledneho poctu
            count += currentTracks->capacity;
            currentTracks = currentTracks->next;
        }
    }
    return count;
}