Find all combinations in 2d array to seat variable amount of people in theater in C?

Question

I have an array of R rows and C columns (Max value of R and C is 50). The program requires that the user inputs the number of number of rows, number of columns of theatre, number people that will view the movie and the program prints all the possible seating combinations.

For example for 2 people , 3 rows , 3 columns

PP*
***
***

P*P
***
***

P**
P**
***

and so on...

The only thing I could figure out is using variable amount of nested loops depending on number of people user inputs and still no idea how to implement it.

Can anyone explain me how to achieve/implement this logic in C?

Answer 1

It seems He doesn't need to distinct between peoples, so it's selecting n seats of R*C seats whose number of possible cases is C(R*C,n)

so for R=2,C=2 and n=2 there should be 6 combinations: 00,11; 01,01; 10,01; 01,10; 10,10; 11,00;

EDIT: nested loop solution:

#include <string.h>
#include <stdio.h>
#include <stdlib.h>

void OutSeats(int *seats,int R, int C, int n)
{
    int i,j,k=0;
#ifdef DEBUG
    for (i=1;i<=n;i++)
        printf("%d,",seats[i]);
    putchar('\n');
#else
    /* It should be alloced only once */
    static int* actual=0;    
    if (!actual)
        actual = calloc(R*C,sizeof(int));
    memset(actual,0,R*C*sizeof(int));
    for (i=1;i<=n;i++)
        actual[seats[i]-1] = 1;

    for (i=0;i<R;i++)
    {
        for (j=0;j<C;j++,k++)
            printf("%d",actual[k]);
        putchar('\n');
    }
    putchar('\n');
#endif
}
/***********************************/
void GenCombination(int R, int C, int n)
{
    int *seats = (int*)malloc((n+1)*sizeof(int));
    int i,sub;
    for (i=1;i<=n;i++)
        seats[i]=i;

    while (1)
    {
        OutSeats(seats,R,C,n);
        if (seats[n]<R*C)
            seats[n]++;
        else
        {
            sub=1;
            while ((sub<n) && (seats[n-sub]>=R*C-sub))
                sub++;
            if (sub<n)
            {
                seats[n-sub]++;
                for (i=n-sub+1 ; i<=n ; i++)
                    seats[i] = seats[i-1] + 1;
            }
            else
                break;
        }
    }

    free(seats);
}
/***********************************/
void main()
{
    int R,C,n;
    printf("Give R,C,n:");
    scanf("%d%d%d",&R,&C,&n);
    GenCombination(R,C,n);
}

Array seats holds seats assigned to each person. GenCombination works like a clock. It increases the last item till it reaches the maximum boundary then moves back and try to increase previous items and again get to the last item. Sequence of assigned seats is always increasing so that unique combinations will be generated. function OutSeats prints seats arrangement by converting assigned seats to actual seats.