[C] struct, union 의 결합

#include 
typedef union {
    double math;
    double phys;
    double chem;
} Score;

typedef struct student {
    char name[10];
    int age;
    Score grade;
    char whichSubject;
} Student;

void input(Student *s) {
    printf("input your name: ");
    scanf("%s", s->name);
    printf("input your age: ");
    scanf("%d", &s->age);
    printf("which subject m/p/c: ");
    scanf(" %c", &s->whichSubject); //<
    switch (s->whichSubject) {
        case 'm': scanf("%lf", &s->grade.math); break;
        case 'p': scanf("%lf", &s->grade.phys); break;
        case 'c': scanf("%lf", &s->grade.chem); break;
    }
}

void print(Student *s) {
    switch (s->whichSubject) {
        case 'm': printf("My name is %s, and I'm %d. I got %f in Math
", s->name, s->age, s->grade.math); break;
        case 'p': printf("My name is %s, and I'm %d. I got %f in Physics
", s->name, s->age, s->grade.phys); break;
        case 'c': printf("My name is %s, and I'm %d. I got %f in Chemistry
", s->name, s->age, s->grade.chem); break;
    }
}

int main( )
{
    Student s1;
    input(&s1);
    print(&s1);
    return 0;
}

//struc, union, array  
#include 
typedef union {
    double math;
    double phys;
    double chem;
} Subject;

typedef struct {
    char name[20];
    int age;
    Subject scores;
    char whichSubject;
} Student;

void input(Student *s, int n) {
    for (int i = 0; i < n; ++i) {
        printf("input your name: ");
        scanf(" %19[^
]", s[i].name); //" %19[^
]"     
        printf("input your age: ");
        scanf("%d", &s[i].age);
        printf("which subject m/p/c: ");
        scanf(" %c", &s[i].whichSubject); //" %c"     
        switch ( s[i].whichSubject ) {
            case 'm': printf("input your math score: "); scanf("%lf", &s[i].scores.math); break;
            case 'p': printf("input your physics score: "); scanf("%lf", &s[i].scores.phys); break;
            case 'c': printf("input your chemistry score: "); scanf("%lf", &s[i].scores.chem); break;
        }
    }
}

double getAve(Student *s, int n) {
    double sum = 0;
    int i;
    for ( i = 0; i < n; ++i ) {
        switch (s[i].whichSubject) {
            case 'm': sum += s[i].scores.math; break;
            case 'p': sum += s[i].scores.phys; break;
            case 'c': sum += s[i].scores.chem; break;
        }
    }
    return sum / n;
}

void display(Student *s, int n) {
    for ( int i = 0; i < n; ++i ) {
        switch (s[i].whichSubject) {
            case 'm': printf("%s's math score is %f
", s[i].name, s[i].scores.math); break;
            case 'p': printf("%s's physics score is %f
", s[i].name, s[i].scores.phys); break;
            case 'c': printf("%s's chemistry score is %f
", s[i].name, s[i].scores.chem); break;
        }
    }
}

int main() {
    const int size = 2;
    Student stu[size];
    input(stu, size);
    printf("average = %f
", getAve(stu, size));
    display(stu, size);
}