#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <time.h>


//  RETURNS A PROBABILITY IN THE RANGE [0.0 .. 1.0]
double PROB(void)
{
    return ((double)rand()/(double)RAND_MAX);
}


//  SIMULATE THE COMMUNICATION, RETURN ITS UTILISATION
double SlottedAloha(int nslots, int nnodes, double ProbNew, double ProbRetry)
{
    double utilisation = 0.0;

//  SIMULATE THE COMMUNICATION
//  ......
//  CALCULATE THE utilisation HERE

    return utilisation;
}


int main(int argc, char *argv[])
{
//  DEFAULT ATTRIBUTES FOR OUR SIMULATION
    int    nslots       = 10000;
    int    nnodes       = 5;
    double ProbNew      = 0.1;
    double ProbRetry    = 0.1;

//  ACCEPT COMMAND-LINE ARGUMENTS TO MODIFY THE DEFAULT ATTRIBUTES
    if(argc == 5) {
        nslots          = atoi(argv[1]);
        nnodes          = atoi(argv[2]);
        ProbNew         = atof(argv[3]);
        ProbRetry       = atof(argv[4]);
    }

//  CHECK THE CHOSEN ATTRIBUTES
    if(nslots<1 || nnodes<1 ||
       ProbNew<0.0 || ProbNew>1.0 || ProbRetry<0.0 || ProbRetry>1.0) {
        fprintf(stderr, "Usage: %s nslots nnodes prob-new prob-Tx\n", argv[0]);
        exit(EXIT_FAILURE);
    }

//  SEED RANDOM NUMBER SEQUENCE
    srand((long)time(NULL));

//  SIMULATE THE COMMUNICATION, PRINT ITS UTILISATION
    printf("%.2f%%\n", 100.0 * SlottedAloha(nslots, nnodes, ProbNew, ProbRetry));

    exit(EXIT_SUCCESS);
    return 0;
}