Übung2

Merged cars.c from my branch to Übung 2 branch

cars.c

+#include <stdio.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <unistd.h>
+
+#define NUM_CARS 2
+#define NUM_CROSSES 100000
+
+pthread_mutex_t bridge_mutex = PTHREAD_MUTEX_INITIALIZER;
+int bridge_count = 0;
+int cross_count = 0;
+
+void *cross_bridge(void *arg) {
+    int id = *(int *) arg;
+    int i;
+    for (i = 0; i < NUM_CROSSES; i++) {
+        // Wait before crossing the bridge
+        usleep(rand() % 10000);
+
+        // Try to acquire the bridge mutex
+        pthread_mutex_lock(&bridge_mutex);
+
+        // Check if the bridge is already occupied
+        if (bridge_count > 0) {
+            printf("Car %d waiting at bridge (cross %d)\n", id, cross_count);
+        }
+
+        // Increment the bridge count
+        bridge_count++;
+
+        // Release the bridge mutex
+        pthread_mutex_unlock(&bridge_mutex);
+
+        // Cross the bridge
+        printf("Car %d crossing bridge (cross %d)\n", id, cross_count);
+        cross_count++;
+        usleep(rand() % 10000);
+
+        // Try to acquire the bridge mutex again
+        pthread_mutex_lock(&bridge_mutex);
+
+        // Decrement the bridge count
+        bridge_count--;
+
+        // Release the bridge mutex
+        pthread_mutex_unlock(&bridge_mutex);
+    }
+    pthread_exit(NULL);
+}
+
+int main() {
+    int i;
+    pthread_t cars[NUM_CARS];
+    int ids[NUM_CARS];
+
+    // Initialize the random number generator
+    srand(time(NULL));
+
+    // Create the cars
+    for (i = 0; i < NUM_CARS; i++) {
+        ids[i] = i + 1;
+        pthread_create(&cars[i], NULL, cross_bridge, &ids[i]);
+    }
+
+    // Wait for the cars to finish
+    for (i = 0; i < NUM_CARS; i++) {
+        pthread_join(cars[i], NULL);
+    }
+
+    return 0;
+}