C++; loop with randomizing array keys not working

Question

I am stuck with a problem that I originally thought would be so easy to solve!

I have an enum with 4 values (empty, male, female, child). I have an array which corresponds to 50 seats. So, I would like to put men, women, and children in the empty seats based on a randomly generated seat number. If the seat is not empty, then the program should continue to search for other empty seats.

This is what I have:

 #include <cstdlib>
 #include <ctime>
 #include <iostream>
 #include <string>

 using namespace std;

    enum pax {E, M, F, C};
    pax seats[50] = {E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E,
                    E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E};

    int paxNumMaleTotal;    // Total number of Male passengers Loaded
    int paxNumFemaleTotal;
    int paxNumChildTotal;

    void random(int j);


    int main()  {


    // Randomize seating for Male

    int n=1;
    int i=0;
    paxNumMaleTotal=35;
    paxNumFemaleTotal=8;
    paxNumChildTotal=5;

        while (n<= paxNumMaleTotal)  {  // loop until all men take their seats

            while (seats[i] != M || seats[i] != F || seats[i] != C)   {  
                   // take a seat unless the seat is not occupied
                 random(i);                 // generate a random seat to be taken
                 seats[i] = M;              // Seat is taken by a man
            }
            n++;  // seat is taken, take the next one

         }


     for (int k=0; k<50; k++)  {     // printing the seating chart
        cout << seats[k] << endl;
        }
 }

 void random(int j)     // this is the function that gives a random seat number
 {
    srand( time( NULL ) );
    j = rand() % 50;
 }

So, I tried all possible options. It either puts men in all 50 seats or, like in this case, put a man in the first seat with no loop. Thanks a lot for your time!

Thanks for your help. Using the reference, I solved the issue of randomly selecting a seat. A problem with the loop is still here. It selects only one seat (randomly) and not 35 seats. :-(

---

EDIT: Thank you! The random_shuffle function did the trick!

for (int i=0; i < paxNumMaleTotal; i++)    {
        seats[i] = M;
}

for (int i = paxNumMaleTotal; i < paxNumFemaleTotal + paxNumMaleTotal; i++)    {
        seats[i] = F;
}

for (int i=paxNumFemaleTotal + paxNumMaleTotal; i < paxNumFemaleTotal + paxNumMaleTotal +
                            paxNumChildTotal; i++)  {
        seats[i] = C;
}

// Randomize seating for passengers
std::random_shuffle (&seats[0], &seats[49]);

Answer 1

This:

srand( time( NULL ) );
j = rand() % 50;

is the problem. time(NULL) has 1 second resolution. This seeds your random generator to almost always the same value, because the outer loop is much faster than one second.

Solution: Initialize your random generator only once at the beginning of the program.

Additionally: your assignement to j has no effect. You modify a copy of the argument and this copy is never returned.

Answer 2

Your random() function does not return anything. You probably meant passing j by reference.