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du6/a_station.h

@@ -0,0 +1,91 @@
+#ifndef STATION_H
+#define STATION_H
+// Pocet trati k dispozicii
+#define STATION_SIZE 10
+// Maximalny pocet znakov pre ulozenie nazvu cielovej stanice
+#define TARGET_SIZE 36
+
+/**
+ * Jeden zaznam o kapacite do cielovej stanice
+ */
+struct car {
+    // Cielova stanica / nazov
+    char value[TARGET_SIZE];
+    // Pocet cestujuchich
+    int capacity;
+    // Smernik na dalsi zaznam
+    struct car* next;
+};
+
+/**
+ * Cela databaza zaznamov
+ */
+struct station {
+    // Dynamicke pole smernikov na zaznamy
+    // jeden zaznam ma typ struct car*
+    struct car** tracks;
+    // Velkost pola tracks
+    int track_count;
+};
+
+
+/**
+ * Vytvori prazdnu stanicu.
+ * Alokuje pole smernikov tracks na pociatocnu kapacitu STATION_SIZE
+ * nastavi velkost capacity na STATION_SIZE
+ * @return smernik na prazdnu stanicu
+ */
+struct station* create_station();
+
+/**
+ * Uvolni pamat
+ * @param smernik na databazu
+ */
+void destroy_station(struct station* station);
+
+/**
+ * Vyberie poziciu v poli station->tracks pre ulozenie zaznamu target
+ *
+ * Proces vyberu by mal splnat kriteria pre hash funkciu:
+ * - rovnaky retazec by mal vzdy mat rovnaky vysledok
+ * - pre rozne retazce by mali byt vysledky co najviac rozne
+ *
+ * @param smernik na databazu
+ * @param nazov cielovej stanice
+ * @return cislo v intervale 0 az N-1, kde N je  station->track_count
+ */
+int select_track(struct station* station, const char* target);
+
+/**
+ * Zvysi zaznam o pocte cestujucich do danej cielovej stanice.
+ *
+ * Najprv sa vyberie cielova trat pomocou select_track(). Ak zaznam neexistuje, 
+ * vytvori sa novy. Ak zaznam na danej trati (spojkovom zozname) existuje, cislo sa pripocita.
+ * V databaze nesmu byt dva zaznamy s rovnakou cielovou stanicou.
+ *
+ * @param smernik na databazu
+ * @param nazov cielovej stanice
+ */
+void add_target_capacity(struct station* station,const char* target, int capacity);
+
+/**
+ * Ziska zaznam o cielovej stanici.
+ * @param smernik na databazu
+ * @param nazov cielovej stanice
+ *
+ * @return kapacitu do cielovej stanice. Ak sa zaznam nenachedza, vrati nula.
+ */
+int get_target_capacity(struct station* station,const char* target);
+
+/**
+ * Spocita pocet cielovych stanic
+ * @param smernik na databazu
+ */
+int count_targets(struct station* station);
+
+/**
+ * Spocita kapacitu vo vsetkych zaznamoch
+ * @param smernik na databazu
+ */
+int count_capacity(struct station* station);
+#endif

du6/program.c

@@ -0,0 +1,104 @@
+#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;
+}
+
+
+/* djb2 hash function by Dan Bernstein - deterministic and simple */
+static unsigned long hash_str(const char *str) {
+    unsigned long hash = 5381;
+    int c;
+    while ((c = (unsigned char)*str++))
+        hash = ((hash << 5) + hash) + c; /* hash * 33 + c */
+    return hash;
+}
+
+void destroy_station(struct station* station){
+    if(!station) return;
+    if(station->tracks){
+        for(int i = 0; i < station->track_count; ++i){
+            struct car* cur = station->tracks[i];
+            while(cur){
+                struct car* next = cur->next;
+                free(cur);
+                cur = next;
+            }
+        }
+        free(station->tracks);
+    }
+    free(station);
+}
+
+int select_track(struct station* station, const char* target){
+    if(!station || !target) return 0;
+    unsigned long h = hash_str(target);
+    return (int)(h % (unsigned long)station->track_count);
+}
+
+void add_target_capacity(struct station* station,const char* target, int capacity){
+    if(!station || !target || capacity == 0) return;
+    int idx = select_track(station, target);
+    struct car* cur = station->tracks[idx];
+    struct car* prev = NULL;
+    while(cur){
+        if(strncmp(cur->value, target, TARGET_SIZE) == 0){
+            cur->capacity += capacity;
+            return;
+        }
+        prev = cur;
+        cur = cur->next;
+    }
+    /* not found -> create new record and append at head for simplicity */
+    struct car* node = (struct car*)calloc(1, sizeof(struct car));
+    if(!node) return; /* allocation failed */
+    strncpy(node->value, target, TARGET_SIZE - 1);
+    node->value[TARGET_SIZE-1] = '\0';
+    node->capacity = capacity;
+    node->next = station->tracks[idx];
+    station->tracks[idx] = node;
+}
+
+int get_target_capacity(struct station* station,const char* target){
+    if(!station || !target) return 0;
+    int idx = select_track(station, target);
+    struct car* cur = station->tracks[idx];
+    while(cur){
+        if(strncmp(cur->value, target, TARGET_SIZE) == 0){
+            return cur->capacity;
+        }
+        cur = cur->next;
+    }
+    return 0;
+}
+
+int count_targets(struct station* station){
+    if(!station) return 0;
+    int count = 0;
+    for(int i = 0; i < station->track_count; ++i){
+        struct car* cur = station->tracks[i];
+        while(cur){
+            count++;
+            cur = cur->next;
+        }
+    }
+    return count;
+}
+
+int count_capacity(struct station* station){
+    if(!station) return 0;
+    int total = 0;
+    for(int i = 0; i < station->track_count; ++i){
+        struct car* cur = station->tracks[i];
+        while(cur){
+            total += cur->capacity;
+            cur = cur->next;
+        }
+    }
+    return total;
+}