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

#define STARTING_FAMILIES 4
#define GENERATIONS 5000000

void
doAGeneration(int dads, int moms, int *boys, int *girls);

int
main()
{
        int             dads, moms, boys, girls;
        int             generation;
        int             total_boys, total_girls;
        float           girl_frac, girl_prop;

        /* initial conditions */
        dads = moms = STARTING_FAMILIES;
        boys = girls = total_boys = total_girls = 0;
        srand(time(NULL));

        for (generation = 0; generation < GENERATIONS; generation ++) {
                doAGeneration(dads, moms, &boys, &girls);
                total_boys += boys;
                total_girls += girls;

                /* commented out code - to test if follow-on generations affect results
                        dads = boys;
                        moms = girls;
                        if ((moms == 0) || (dads == 0))
                                break;
                */

                boys = girls = 0;
        }

        /* calculate and print overall stats */
        girl_frac =
                100 * (float) total_girls
                /
                ((float) total_girls + (float) total_boys);
        girl_prop = (float) total_girls / (float) total_boys;

        printf("\npopulation %d\n", total_boys + total_girls);
        printf("%d total boys,\n%d total girls,\n%f %%girls,\n%f girls/boy\n",
                        total_boys, total_girls, girl_frac, girl_prop);

        return 0;
}

void
doAGeneration(int dads, int moms, int *boys, int *girls)
{
        int             families;
        int             gender;
        int             i;

        if (dads < moms)
                families = dads;
        else
                families = moms;

        /* Generate children for each family */
        for (i = 0; i < families; i++) {
                gender = 0;
                while (gender == 0) {
                        gender = rand() % 2;
                        if (gender == 0)
                                (*girls)++;
                        else
                                (*boys)++;
                }
        }
        /* Debugging print
                printf("%d girls, %d boys generated\n", *girls, *boys);
        */
}