MP4

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

int values(int *pop, double *rate);
void reportgen(int pop, double rate);

int main()
{
    int initial_pop;
    double infect_rate;

    printf("Zombie Infection Model\n");
    values(&initial_pop, &infect_rate);
    reportgen(initial_pop, infect_rate);
    printf("Report generated!\n");
    return 0;
}
/* values - user enters population greater than 0 and rate between 0 and 1 */
int values(int *pop, double *rate)
{
    int p;
    double r;

    while(1)
    {
    printf("Please enter initial population:");
    scanf("%d", &p);
        if (p >= 0)
        {
            while(1)
            {
                *pop = p;
                printf("Please enter infection rate as a decimal (e.g. 25% = 0.25):");
                scanf("%lf", &r);
                if (r > 0.0 && r < 1.0)
                {
                    *rate = r;
                    return(0);
                }
                    else
                        printf("Infection rate must be between 0 and 1 inclusive. Try again.\n");
            }
        }
        else
            {
                printf("Population must be non-negative. Try again.\n");
            }
    }
}
void reportgen(int pop, double rate)
{
    FILE* out_file;
    out_file = fopen("modelOutput.txt", "w");
    int time = 1;
    int infected_pop = 1.0;
    int surviving_pop = pop;
    double delta = 0;
    int deltafinal = 0;
    fprintf(out_file, " Time	      Humans	     Zombies\n");
    while (deltafinal < surviving_pop)
    {
    surviving_pop = (surviving_pop-deltafinal);
    infected_pop = (infected_pop+deltafinal);
    delta = (rate*surviving_pop*infected_pop);
    deltafinal = delta;
    fprintf(out_file, "%5d\t%12d\t%12d\n", time, surviving_pop, infected_pop);
    time=(time+1);
    }
    surviving_pop = 0;
    infected_pop = (pop + 1);
    fprintf(out_file, "%5d\t%12d\t%12d\n", time, surviving_pop, infected_pop);
}