TriangleCalc

#include <stdio.h>
#include <math.h>

int triangle(double a, double b, double c, double* P, double* S){
    // 0 -> ok, -1 -> nok
    if (a<=0 ||b<=0 ||c<=0 || a+b<=c || a+c<=b || b+c<=a){
        return -1;
    }
    *P = a + b + c;
    double p = *P / 2.0;
    *S = sqrt(p*(p-a)*(p-b)*(p-c));
    return 0;
}

int main(){
    double a, b, c, P, S;
    while (scanf("%lf %lf %lf", &a, &b, &c) != EOF){
        if (triangle(a, b, c, &P, &S) == -1){
            fprintf(stderr, "Invalid triangle sides!\n");
        } else {
            printf("P = %.2lf, S = %.2lf\n", P, S);
        }
    }
    return 0;
}