123

du6/a_station.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;
+}