Semaphore Exercise

NS-cars.candEW-cars.care two programs that simulate traffic control. When North-South cars past the crossroads, they should ensure that road from north to south is available, if north-south road is not available, they keep waiting. This is similar to East-West cars. Please addsemaphore synchronizationin these two programs so that North-South cars and Easts-West cars can past the crossroads alternately and there will not be car accident. Note that when north-south road is available, east-west road is not available.

/*NS-cars.c*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int main(int argc, char * argv[])
{
    int i, car=0, loop=3;
    for(i=0;i<loop;i++){
        printf("Semaphore: The road from north to south is open\n");
        sleep(1);
        printf("NS-Car: car %d passed\n",car++);
    }
    printf("NS: Time is up. %d cars passed.\n",car);
    return 0;
}

/*EW-cars.c*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int main(int argc, char * argv[])
{
    int i,car=0, loop=3;
    for(i=0;i<loop;i++){
        printf("Semaphore: The road from east to west is open\n");
        sleep(rand()%2+1);
        printf("EW-Car: car %d passed\n",car++);
    }
    printf("EW: Time is up. %d cars passed.\n",car);
    return 0;
}